Refactor type hints and clean up imports in crew.py (#2480)

- Removed unused import of BaseTool from langchain_core.tools.
- Updated type hints in crew.py to streamline code and improve readability.
- Cleaned up whitespace for better code formatting.

Co-authored-by: Brandon Hancock (bhancock_ai) <109994880+bhancockio@users.noreply.github.com>

src/crewai/crew.py

@@ -6,9 +6,8 @@ import warnings
 from concurrent.futures import Future
 from copy import copy as shallow_copy
 from hashlib import md5
-from typing import Any, Callable, Dict, List, Optional, Set, Tuple, TypeVar, Union, cast
+from typing import Any, Callable, Dict, List, Optional, Set, Tuple, Union, cast
 
-from langchain_core.tools import BaseTool as LangchainBaseTool
 from pydantic import (
     UUID4,
     BaseModel,