Reinstate the API changes check in the workflow

[jtpio]

Issue to track the following TODO:

lumino/.github/workflows/check-api-changes.yml

Lines 53 to 64 in 7251957

	# TODO: re-enable check for the following files:
	# review/api/*.api.md
	# - name: Get API changes
	# id: api-changed
	# - name: Fail if API are modified
	# if: steps.api-changed.outputs.any_changed == 'true'
	# run: |
	# for file in ${{ steps.api-changed.outputs.all_changed_files }}; do
	# echo "$file"
	# done
	# exit 1

[fcollonval]

In the language packs repo, we are directly using git status:

https://github.com/jupyterlab/language-packs/blob/93202104868319eec841161b360376a75c8da930/.github/workflows/update_pot.yml#L41

I guess we can drop the dummy commit and do a similar test on api files to fix this issue.