fix: fix missing import in _default.py (#1015)

* fix: missing import in _default.py

* chore: update sys test creds

Author: arithmetic1728

packages/google-auth/google/auth/_default.py

@@ -554,6 +554,8 @@ def default(scopes=None, request=None, quota_project_id=None, default_scopes=Non
                 getattr(credentials, "get_project_id", None)
             ):
                 if request is None:
+                    import google.auth.transport.requests
+
                     request = google.auth.transport.requests.Request()
                 project_id = credentials.get_project_id(request=request)