feat: disable grammar restrictions within reasoning sections (#4984)

Co-authored-by: tianhaoyu <thy@mail.ecust.edu.cn>
Co-authored-by: DarkSharpness <2040703891@qq.com>

python/sglang/srt/constrained/xgrammar_backend.py

@@ -48,6 +48,7 @@ class XGrammarGrammar(BaseGrammarObject):
         ctx: CompiledGrammar,
         override_stop_tokens: Optional[Union[List[int], int]],
     ) -> None:
+        super().__init__()
         self.matcher = matcher
         self.vocab_size = vocab_size
         self.ctx = ctx