Fix: Qwen3CoderHandler import in BFCL model_config

[yooooo00]

• Running bfcl generate --model Qwen3-Coder-480B-A35B-Instruct --num-threads 8 fails with:

Traceback (most recent call last):
  File "/root/.local/bin/bfcl", line 5, in <module>
    from bfcl_eval.__main__ import cli
  File "/root/work/filestorage/cyy/Qwen3-Coder/Qwen3-Coder-main/qwencoder-eval/tool_calling_eval/berkeley-function-call-leaderboard/bfcl_eval/__main__.py", line 9, in <module>
    from bfcl_eval._llm_response_generation import main as generation_main
  File "/root/work/filestorage/cyy/Qwen3-Coder/Qwen3-Coder-main/qwencoder-eval/tool_calling_eval/berkeley-function-call-leaderboard/bfcl_eval/_llm_response_generation.py", line 19, in <module>
    from bfcl_eval.eval_checker.eval_runner_helper import load_file
  File "/root/work/filestorage/cyy/Qwen3-Coder/Qwen3-Coder-main/qwencoder-eval/tool_calling_eval/berkeley-function-call-leaderboard/bfcl_eval/eval_checker/eval_runner_helper.py", line 11, in <module>
    from bfcl_eval.constants.model_config import MODEL_CONFIG_MAPPING
  File "/root/work/filestorage/cyy/Qwen3-Coder/Qwen3-Coder-main/qwencoder-eval/tool_calling_eval/berkeley-function-call-leaderboard/bfcl_eval/constants/model_config.py", line 1678, in <module>
    model_handler=Qwen3CoderHandler,
                  ^^^^^^^^^^^^^^^^^
NameError: name 'Qwen3CoderHandler' is not defined. Did you mean: 'QwenFCHandler'?