Clarify GCS URL signing limitations on GCE (#6104)
Clarify GCS URL signing limitations on GCE (#6104)

The line 'If you are on Google Compute Engine, you can't generate a signed URL' wrongly implies URL generation is impossible from GCE. Adding clarification that this line only holds true when GCE is using GCE service account.


googleapis/python-storage,googleapis/python-storage