Fix devcontainer smoke test for forked repos

When we run the smoke test on main, we push the devcontainer images to ghcr to be used as a cache for future workflow runs. This causes an error on forks because they don't have permission to push (which is good). So, let's set the step to never push if the repo is a fork. The github context doesn't have a way of checking if the repo is a fork, so I check the repo owner instead, but that's ok since it's the repo owner (rails) who has permissions to push the package.

.github/workflows/devcontainer-smoke-test.yml

@@ -46,5 +46,6 @@ jobs:
           imageName: ghcr.io/rails/smoke-test-devcontainer
           cacheFrom: ghcr.io/rails/smoke-test-devcontainer
           imageTag: ${{ matrix.DATABASE }}
+          push: ${{ github.repository_owner == 'rails' && 'filter' || 'never' }}
           refFilterForPush: refs/heads/main
           runCmd: bin/rails g scaffold Post && bin/rails db:migrate && bin/rails test