chore(firestore): release 1.6.0 (googleapis#9621)

* Release firestore 1.6.0

* Update firestore/CHANGELOG.md

Co-Authored-By: Tres Seaver <tseaver@palladion.com>

chore(containeranalysis): release 0.3.1 (googleapis#9636)

chore(cloudbuild): release 0.1.0 (googleapis#9635)

chore(tasks): release 1.3.0 (googleapis#9595)

chore(storage): release 1.22.0 (googleapis#9604)

Closes googleapis#9603.

chore(automl): release 0.7.1 (googleapis#9566)

chore(asset): release 0.5.0 (googleapis#9567)

chore(storage): release 1.21.0 (googleapis#9553)

chore(translate): release 2.0.0 (googleapis#9527)

chore(spanner): release 1.12.0 (googleapis#9530)