chore(deps): update dependency google-cloud-pubsub to v1.5.0 [(#3781)](GoogleCloudPlatform/python-docs-samples#3781)

Co-authored-by: Bu Sun Kim <[email protected]>

Author: 2 people

samples/snippets/requirements.txt

@@ -1 +1 @@
-google-cloud-pubsub==1.4.3
+google-cloud-pubsub==1.5.0