Update dependency google-cloud-pubsub to v1.4.2 (#3335)

Co-authored-by: Tianzi Cai <[email protected]>
Co-authored-by: Leah E. Cole <[email protected]>

Author: 3 people

appengine/flexible/pubsub/requirements.txt

@@ -1,3 +1,3 @@
 Flask==1.1.1
-google-cloud-pubsub==1.1.0
+google-cloud-pubsub==1.4.2
 gunicorn==20.0.4

appengine/standard_python37/pubsub/requirements.txt

@@ -1,4 +1,4 @@
 Flask==1.1.1
 google-api-python-client==1.7.11
 google-auth==1.11.2
-google-cloud-pubsub==1.1.0
+google-cloud-pubsub==1.4.2