Fix nightly images (#1026)

* Fix outdated context name

Signed-off-by: Aaron Chong <aaronchong@google.com>

* Revert trigger on push

Signed-off-by: Aaron Chong <aaronchong@google.com>

---------

Signed-off-by: Aaron Chong <aaronchong@google.com>

Author: aaronchongth

.github/workflows/nightly.yml

@@ -52,7 +52,7 @@ jobs:
           build-args: |
             BASE_IMAGE=ghcr.io/${{ github.repository }}/minimal-rmf:rolling
           tags: ghcr.io/${{ github.repository }}/demo-dashboard:latest
-          context: .github/dashboard
+          context: .github/demo-dashboard
   build-api-server-image:
     needs: build-minimal-rmf-docker-images
     name: Push API server docker image to GitHub Packages