Add missing import to Raytune docs (#17683)

Co-authored-by: UltralyticsAssistant <web@ultralytics.com>

docs/en/integrations/ray-tune.md

@@ -106,6 +106,8 @@ In this example, we demonstrate how to use a custom search space for hyperparame
 !!! example "Usage"
 
     ```python
+    from ray import tune
+
     from ultralytics import YOLO
 
     # Define a YOLO model