chore: stop sending notification for update python requirements on unchanged

[leangseu-edx]

Description:

• This is to stop the workflow to send notification on requirement unchanged.

Note: If we want to have specific output for this case, we can add additional output on https://github.com/openedx/testeng-ci/blob/ed9083cd6f0a774d5de75cefd356ad69dd47b9bf/jenkins/pull_request_creator.py#L224. However, I think this should be enough.