Fix lint errors: Remove unused imports

- Remove unused contextlib, sys, threading, io, TextIO imports from llm.py
- Remove unused importlib import from test_sys_stream_hijacking.py
- Address Ruff lint failures from CI

Co-Authored-By: João <joao@crewai.com>

src/crewai/llm.py

@@ -1,9 +1,6 @@
-import contextlib
 import json
 import logging
 import os
-import sys
-import threading
 import warnings
 from collections import defaultdict
 from contextlib import contextmanager
@@ -49,8 +46,7 @@ with warnings.catch_warnings():
     from litellm.utils import supports_response_schema
 
 
-import io
-from typing import TextIO
+
 
 from crewai.llms.base_llm import BaseLLM
 from crewai.utilities.events import crewai_event_bus

tests/test_sys_stream_hijacking.py

@@ -2,7 +2,6 @@
 
 import sys
 import io
-import importlib
 from unittest.mock import patch