Revert "fix: update `_GOOGLE_OAUTH2_CERTS_URL` (#365)" (#444)
Revert "fix: update `_GOOGLE_OAUTH2_CERTS_URL` (#365)" (#444)

This reverts commit 054db75734756b0e82e7984ca07fa80025edc908.
googleapis/google-auth-library-python,googleapis/google-auth-library-python