fix(qqbot): correct Authorization header format in send_message REST path (#11569)

The send_message tool's direct-REST QQBot path used "QQBotAccessToken {token}"
which QQ's API rejects with 401. The correct format is "QQBot {token}" — the
gateway adapter at gateway/platforms/qqbot.py uses this format in all 5 header
sites (lines 341, 551, 579, 1068, 1467); this was the one outlier.

Credit to @Quon for surfacing this in #10257 (that PR had unrelated issues in
its media-upload logic and was closed; this salvages the genuine 1-line fix).

tools/send_message_tool.py

@@ -1274,7 +1274,7 @@ async def _send_qqbot(pconfig, chat_id, message):
 
             # Step 2: Send message via REST
             headers = {
-                "Authorization": f"QQBotAccessToken {access_token}",
+                "Authorization": f"QQBot {access_token}",
                 "Content-Type": "application/json",
             }
             url = f"https://api.sgroup.qq.com/channels/{chat_id}/messages"