fix: replace asyncio.iscoroutinefunction with inspect.iscoroutinefunction

- asyncio.iscoroutinefunction() is deprecated in Python 3.16
- Use inspect.iscoroutinefunction() instead (standard library function)
- Removes deprecation warning in track_llm_api_timing decorator

This is part of the broader effort to remove Python 3.16 deprecation warnings.

litellm/litellm_core_utils/logging_utils.py

@@ -1,5 +1,6 @@
 import asyncio
 import functools
+import inspect
 import time
 from datetime import datetime
 from typing import TYPE_CHECKING, Any, List, Optional, Union
@@ -270,7 +271,7 @@ def track_llm_api_timing():
                     verbose_logger.debug(f"Error in service logging: {str(e)}")
 
         # Check if the function is async or sync
-        if asyncio.iscoroutinefunction(func):
+        if inspect.iscoroutinefunction(func):
             return async_wrapper
         return sync_wrapper