chore(bigtable/firestore/datastore): consolidating DB reviewers (#5982)
chore(bigtable/firestore/datastore): consolidating DB reviewers (#5982)

* chore(bigtable/firestore/datastore): consolidating DB reviewers

* fix: remove garye from CODEOWNERS
googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go