Remove default None value from LMPOP (#2438)

Author: dvora-h

redis/commands/core.py

@@ -2553,7 +2553,7 @@ def lmpop(
         self,
         num_keys: int,
         *args: List[str],
-        direction: str = None,
+        direction: str,
         count: Optional[int] = 1,
     ) -> Union[Awaitable[list], list]:
         """