Add comment to AdAccount read_records method

Author: lazebnyi

airbyte-integrations/connectors/source-facebook-marketing/source_facebook_marketing/streams.py

@@ -312,6 +312,7 @@ def read_records(
         stream_state: Mapping[str, Any] = None,
     ) -> Iterable[Mapping[str, Any]]:
         """Main read method used by CDK"""
+        # FacebookResponse variable _json is link to response in json format
         yield self._api.account.api_get(params=self.request_params(stream_state=stream_state)).__dict__["_json"]