Fix logger caching test: Reset global state for consistent testing

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

tests/test_sys_stream_hijacking.py

@@ -139,7 +139,12 @@ def test_concurrent_llm_calls():
 def test_logger_caching_performance():
     """Test that logger instance is cached for performance."""
     from crewai.llm import suppress_litellm_output
+    import crewai.llm
     
+    original_logger = crewai.llm._litellm_logger
+    crewai.llm._litellm_logger = None
+    
+    try:
         with patch('logging.getLogger') as mock_get_logger:
             mock_logger = MagicMock()
             mock_get_logger.return_value = mock_logger
@@ -151,6 +156,8 @@ def test_logger_caching_performance():
                 pass
                 
             mock_get_logger.assert_called_once_with("litellm")
+    finally:
+        crewai.llm._litellm_logger = original_logger
 
 
 def test_suppression_error_handling():