text: Title: Add `[obsoletes]` to setup
  Body: See https://github.com/googleapis/python-bigquery-sqlalchemy/blob/ac25c4c70767ca85ce5934136b4d074e8ae2ed89/setup.py#L99
  
  We should add a line saying that this replaces `gsheetsdb` (https://pypi.org/project/gsheetsdb/).