fix: update `_GOOGLE_OAUTH2_CERTS_URL` (#365)

* Update _GOOGLE_OAUTH2_CERTS_URL

OpenID Config lists jwks_uri as https://www.googleapis.com/oauth2/v3/certs

https://accounts.google.com/.well-known/openid-configuration
diff --git a/google/oauth2/id_token.py b/google/oauth2/id_token.py
index bc48445..e80c48f 100644
--- a/google/oauth2/id_token.py
+++ b/google/oauth2/id_token.py
@@ -67,7 +67,7 @@
 
 # The URL that provides public certificates for verifying ID tokens issued
 # by Google's OAuth 2.0 authorization server.
-_GOOGLE_OAUTH2_CERTS_URL = "https://www.googleapis.com/oauth2/v1/certs"
+_GOOGLE_OAUTH2_CERTS_URL = "https://www.googleapis.com/oauth2/v3/certs"
 
 # The URL that provides public certificates for verifying ID tokens issued
 # by Firebase and the Google APIs infrastructure