Fix lint and type-checker issues in OAuth2 implementation

- Remove unused imports (List, Optional, MagicMock)
- Fix type annotation: change 'any' to 'Any' in oauth2_token_manager.py
- All OAuth2 tests still pass after fixes

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

tests/test_oauth2_llm.py

@@ -4,7 +4,7 @@ import requests
 import tempfile
 import time
 from pathlib import Path
-from unittest.mock import Mock, patch, MagicMock
+from unittest.mock import Mock, patch
 from crewai.llm import LLM
 from crewai.llms.oauth2_config import OAuth2Config, OAuth2ConfigLoader
 from crewai.llms.oauth2_token_manager import OAuth2TokenManager