chore(deps): update dependency google-auth to v1.21.2 (#84)

Author: renovate-bot

dataproc/snippets/requirements.txt

@@ -1,5 +1,5 @@
 grpcio==1.31.0
-google-auth==1.20.1
+google-auth==1.21.2
 google-auth-httplib2==0.0.4
 google-cloud==0.34.0
 google-cloud-storage==1.30.0