fix remove_message_count not int when restoring from DDB

Author: jeromevdl

src/strands/agent/conversation_manager/conversation_manager.py

@@ -40,7 +40,7 @@ def restore_from_session(self, state: dict[str, Any]) -> Optional[list[Message]]
         """
         if state.get("__name__") != self.__class__.__name__:
             raise ValueError("Invalid conversation manager state.")
-        self.removed_message_count = state["removed_message_count"]
+        self.removed_message_count = int(state["removed_message_count"])
         return None
 
     def get_state(self) -> dict[str, Any]: