Fix wrong docstring

Author: Pijukatel

src/apify/storage_clients/_apify/_request_queue_shared_client.py

@@ -360,7 +360,7 @@ async def _ensure_head_is_non_empty(self) -> None:
         await self._list_head()
 
     async def _get_or_hydrate_request(self, request_id: str) -> Request | None:
-        """Get a request by unique key, either from cache or by fetching from API.
+        """Get a request by id, either from cache or by fetching from API.
 
         Args:
             request_id: Id of the request to get.