fix: preserve whitespace when splitting long qqofficial messages

Author: wcqqq1214

astrbot/core/platform/sources/qqofficial/qqofficial_message_event.py

@@ -243,7 +243,7 @@ def _split_message(cls, text: str) -> list[str]:
                     break
 
             chunks.append(remaining[:split_point])
-            remaining = remaining[split_point:].lstrip()
+            remaining = remaining[split_point:]
 
         return chunks