[post-migration] docs cleanup #16039
Description
Summary of the issues
Cross-linked references
As part of the migration to the google-cloud-python mono-repo, several internal cross-references in the docs no longer worked (largely due to inline links to deleted samples).
A deeper look should be given to the deleted files OR references to see whether there is value in reconstituting those links.
google-cloud-bigquery:
See commit: a62aa46
Reproduce directions, as needed
The following directions were removed from the python-bigquery-sqlalchemy split repo during migration and may need to be reproduced in our release documentation. Confirm what the correct disposition of these instructions should be.
python-bigquery-sqlalchemy
See commit: 9b3bdc1