update TODO comment

Author: parthea

google/api_core/operations_v1/transports/rest_asyncio.py

@@ -129,6 +129,10 @@ def __init__(
             client_info=client_info,
             always_use_jwt_access=always_use_jwt_access,
         )
+        # TODO(https://github.com/googleapis/python-api-core/issues/708): add support for
+        # `default_host` in AsyncAuthorizedSession for feature parity with the synchronous
+        # code.
+        self._session = AsyncAuthorizedSession(self._credentials)
         self._prep_wrapped_messages(client_info, is_async=True)
         self._http_options = http_options or {}
         self._path_prefix = path_prefix