remove --break-system-packages and address docker build warnings.

[fujitatomoya]

closes #5020

the problem can be reproduced with my local environment, and it can be fixed with this patch.

before (original issue)

tomoyafujita@~/DVT/03_OSS/github.com/ros2/ros2_documentation >docker build --rm -f ./docker/image/Dockerfile -t ros2doc:latest .
[+] Building 0.3s (11/11) FINISHED                                                                           docker:default
 => [internal] load build definition from Dockerfile                                                                   0.0s
 => => transferring dockerfile: 1.00kB                                                                                 0.0s
 => WARN: LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 11)      0.0s
 => WARN: LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 12)      0.0s
 => WARN: JSONArgsRecommended: JSON arguments recommended for CMD to prevent unintended behavior related to OS signal  0.0s
 => [internal] load metadata for docker.io/library/ubuntu:jammy                                                        0.0s
 => [internal] load .dockerignore                                                                                      0.0s
 => => transferring context: 2B                                                                                        0.0s
 => [1/7] FROM docker.io/library/ubuntu:jammy                                                                          0.0s
 => CACHED [2/7] RUN if id -u 1000 ; then userdel `id -un 1000` ; fi                                                   0.0s
 => CACHED [3/7] RUN apt-get update &&     apt-get install --no-install-recommends -y         git-all         graphvi  0.0s
 => CACHED [4/7] RUN locale-gen en_US en_US.UTF-8                                                                      0.0s
 => CACHED [5/7] RUN update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8                                                 0.0s
 => CACHED [6/7] RUN useradd -u 1000 -m rosindex                                                                       0.0s
 => CACHED [7/7] WORKDIR /tmp/doc_repository                                                                           0.0s
 => exporting to image                                                                                                 0.0s
 => => exporting layers                                                                                                0.0s
 => => writing image sha256:b7b46e3f5c511d3981499cd011c3abf4057d3ea850651bac7e8c693f8cad0f39                           0.0s
 => => naming to docker.io/library/ros2doc:latest                                                                      0.0s

 3 warnings found (use docker --debug to expand):
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 11)
 - LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 12)
 - JSONArgsRecommended: JSON arguments recommended for CMD to prevent unintended behavior related to OS signals (line 37)

tomoyafujita@~/DVT/03_OSS/github.com/ros2/ros2_documentation >docker run --rm -v /home/tomoyafujita/DVT/03_OSS/github.com/ros2/ros2_documentation:/tmp/doc_repository ros2doc:latest

Usage:
  pip3 install [options] <requirement specifier> [package-index-options] ...
  pip3 install [options] -r <requirements file> [package-index-options] ...
  pip3 install [options] [-e] <vcs project url> ...
  pip3 install [options] [-e] <local project path> ...
  pip3 install [options] <archive url/path> ...

no such option: --break-system-packages

after (with this PR)

tomoyafujita@~/DVT/03_OSS/github.com/ros2/ros2_documentation >docker build --rm -f ./docker/image/Dockerfile -t ros2doc:latest .
[+] Building 0.3s (11/11) FINISHED                                                                           docker:default
 => [internal] load build definition from Dockerfile                                                                   0.0s
 => => transferring dockerfile: 995B                                                                                   0.0s
 => [internal] load metadata for docker.io/library/ubuntu:jammy                                                        0.0s
 => [internal] load .dockerignore                                                                                      0.0s
 => => transferring context: 2B                                                                                        0.0s
 => [1/7] FROM docker.io/library/ubuntu:jammy                                                                          0.0s
 => CACHED [2/7] RUN if id -u 1000 ; then userdel `id -un 1000` ; fi                                                   0.0s
 => CACHED [3/7] RUN apt-get update &&     apt-get install --no-install-recommends -y         git-all         graphvi  0.0s
 => CACHED [4/7] RUN locale-gen en_US en_US.UTF-8                                                                      0.0s
 => CACHED [5/7] RUN update-locale LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8                                                 0.0s
 => CACHED [6/7] RUN useradd -u 1000 -m rosindex                                                                       0.0s
 => CACHED [7/7] WORKDIR /tmp/doc_repository                                                                           0.0s
 => exporting to image                                                                                                 0.0s
 => => exporting layers                                                                                                0.0s
 => => writing image sha256:f4bd8cc7979467ab004c8a1c71fd0d871cf3eb93c47d9b3375c21b857691a82f                           0.0s
 => => naming to docker.io/library/ros2doc:latest                                                                      0.0s

tomoyafujita@~/DVT/03_OSS/github.com/ros2/ros2_documentation >docker run --rm -v /home/tomoyafujita/DVT/03_OSS/github.com/ros2/ros2_documentation:/tmp/doc_repository ros2doc:latest
...(build all targets)

[github-actions]

HTML artifacts: https://github.com/ros2/ros2_documentation/actions/runs/13335224542/artifacts/2594424763.

To view the resulting site:

1. Click on the above link to download the artifacts archive
2. Extract it
3. Open html-artifacts-5021/index.html in your favorite browser

[fujitatomoya]

@christophebedard thank you very much for your help!