Update version number to 0.4.0 (googleapis#8204)

Release 1.13.0 (googleapis#8203)

Release google-cloud-core 1.0.1 (googleapis#8184)

Release google-api-core 1.11.1 (googleapis#8183)

Release bigquery 1.12.1 (googleapis#8084)

* Release 1.12.1

Release bigquery_storage 0.5.0 (googleapis#8038)

* Release 0.5.0

* Remove googleapis#7879 and googleapis#7921 from changelog, since they cancel out.

Release translate-1.5.0 (googleapis#8012)

Release trace-0.21.0 (googleapis#8011)

Release storage-1.16.0 (googleapis#8010)

Release spanner-1.9.0 (googleapis#8009)