* Use PR number directly in netlify github action
Looks like we can get the PR number for the workflow run that triggered
the workflow_run event, so there's no need for the massive faff we were
doing here.
* No need to create pr.json anymore
Switch to upstream and use a more recent version.
Fixes failure to edit on empty descriptions.
Signed-off-by: Alexandre Franke <alexandre.franke@gmail.com>