Pin jsonschema to v3

[atharva-2001]

TARDIS tests were failing because a few methods in jsonschema have been removed as per their deprecation policy.
This PR pins jsonschema to a previous version so that tests can run.

Description

The test with jsonschema v4.0.1 failed and the one with v3.2.0 passed. This PR pins jsonschema to v3, which should allow tests to pass. For reference, please compare recent jsonschema releases here: https://github.com/Julian/jsonschema/releases

Motivation and context

Also fixes #1807

How has this been tested?

• Testing pipeline.
• Other.

Examples

Type of change

• Bug fix.
• New feature.
• Breaking change.
• None of the above.

Checklist

• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
  • (optional) I have built the documentation on my fork following the instructions.
• I have assigned and requested two reviewers for this pull request.

[codecov]

Codecov Report

Merging #1806 (d4fbe0c) into master (e6a8af2) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1806   +/-   ##
=======================================
  Coverage   58.38%   58.38%           
=======================================
  Files          66       66           
  Lines        6705     6705           
=======================================
  Hits         3915     3915           
  Misses       2790     2790           

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[tardis-bot]

Before a pull request is accepted, it must meet the following criteria:

• Is the necessary information provided?
• Is this a duplicate PR?
  • If a new PR is clearly a duplicate, ask how this PR is different from the original PR?
  • If this PR is about to be merged, close the original PR with a link to this new PR that solved the issue.
• Does it pass existing tests and are new tests provided if required?
  • The test coverage should not decrease, and for new features should be close to 100%.
• Is the code tidy?
  • No unnecessary print lines or code comments.

[andrewfullard]

Thanks for discovering the fix

[epassaro]

If this solves the problem, do not pin jsonschema so hard. It's enough to do jsonschema=3. And point out the issue in a comment, otherwise we don't know why some dependencies are pinned.

EDIT: also remember the conda-forge recipe is independent from the environment file located in the tardis repo, so this must be changed there too.