Fix circular import for lm_eval (#6572)

Co-authored-by: Guang Yang <[email protected]>

Author: guangy10

examples/models/llama/eval_llama_lib.py

@@ -20,7 +20,6 @@
     Tokenizer as SentencePieceTokenizer,
 )
 from executorch.extension.llm.tokenizer.utils import get_tokenizer
-from lm_eval.api.model import LM
 from lm_eval.evaluator import simple_evaluate
 
 from .evaluate.eager_eval import EagerEvalWrapper
@@ -159,7 +158,7 @@ def _model_call(self, inps):
 def gen_eval_wrapper(
     model_name: str,
     args: argparse.ArgumentParser,
-) -> LM:
+):
     """
     Generates a wrapper interface around the provided model and tokenizer for
     the lm-evaluation-harness library.