Fix: exception order

Author: rajeshvelicheti

src/a2a/utils/telemetry.py

@@ -165,7 +165,7 @@ async def async_wrapper(*args, **kwargs) -> Any:
 
             # asyncio.CancelledError extends from BaseException
             except asyncio.CancelledError as ce:
-                exception = None
+                exception = ce
                 logger.debug(f'CancelledError in span {actual_span_name}')
                 span.record_exception(ce)
                 raise