chore(deps): update dependency google-cloud-pubsub to v2.9.0 (#249)

Author: renovate-bot

bigquery-datatransfer/snippets/requirements-test.txt

@@ -1,4 +1,4 @@
 google-cloud-bigquery==2.30.1
-google-cloud-pubsub==2.8.0
+google-cloud-pubsub==2.9.0
 pytest==6.2.5
 mock==4.0.3