fix: expiry in compute_engine.IDTokenCredentials

fixes #1323

Author: juzna

google/auth/compute_engine/credentials.py

@@ -389,7 +389,7 @@ def _call_metadata_identity_endpoint(self, request):
             six.raise_from(new_exc, caught_exc)
 
         _, payload, _, _ = jwt._unverified_decode(id_token)
-        return id_token, datetime.datetime.fromtimestamp(payload["exp"])
+        return id_token, datetime.datetime.utcfromtimestamp(payload["exp"])
 
     def refresh(self, request):
         """Refreshes the ID token.