message send: Fix incorrect field types in SendMessageRequest class.

The `local_id` and `queue_id` parameters are actually accepted as strings,
not integers, by the API.
This was introduced in 2fa33be683.

zerver/lib/message.py

@@ -90,8 +90,8 @@ class UnreadMessagesResult(TypedDict):
 class SendMessageRequest:
     message: Message
     stream: Optional[Stream]
-    local_id: Optional[int]
-    sender_queue_id: Optional[int]
+    local_id: Optional[str]
+    sender_queue_id: Optional[str]
     realm: Realm
     mention_data: MentionData
     active_user_ids: Set[int]