Update dependency google-auth to v1.30.1

Author: renovate-bot

requirements.txt

@@ -3,7 +3,7 @@ certifi==2020.6.20
 cffi==1.14.2
 chardet==3.0.4
 google-api-core==1.22.1
-google-auth==1.20.1
+google-auth==1.30.1
 google-cloud-core==1.4.1
 google-cloud-storage==1.30.0
 google-crc32c==0.1.0