chore(deps): update dependency google-cloud-pubsub to v2.13.6 (#604)

Author: renovate-bot

samples/snippets/requirements.txt

@@ -1,4 +1,4 @@
 google-cloud-logging==3.2.1
 google-cloud-bigquery==3.3.1
 google-cloud-storage==2.5.0
-google-cloud-pubsub==2.13.5
+google-cloud-pubsub==2.13.6