chore(deps): update dependency google-cloud-pubsub to v2.4.2 (#288)

Author: renovate-bot

samples/snippets/requirements.txt

@@ -1,4 +1,4 @@
 google-cloud-logging==2.3.1
 google-cloud-bigquery==2.16.0
 google-cloud-storage==1.38.0
-google-cloud-pubsub==2.4.1
+google-cloud-pubsub==2.4.2