chore(deps): update dependency google-auth to v1.18.0 (#4282)

Author: renovate-bot

run/markdown-preview/requirements-test.txt

@@ -1,3 +1,3 @@
 pytest==5.3.2
-google-auth==1.14.0
+google-auth==1.18.0
 google-api-python-client==1.9.3