Remove <think> for KG extraction. (#5027)

### What problem does this PR solve?

#4946

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

graphrag/general/extractor.py

 #
 import logging
 import os
+import re
 from collections import defaultdict, Counter
 from concurrent.futures import ThreadPoolExecutor
 from copy import deepcopy
         if response:
             return response
         response = self._llm.chat(system, hist, conf)
+        response = re.sub(r"<think>.*</think>", "", response)
         if response.find("**ERROR**") >= 0:
             raise Exception(response)
         set_llm_cache(self._llm.llm_name, system, response, history, gen_conf)