Add YOLOv5n to Reproduce section (#6619)

tutorial.ipynb

@@ -983,7 +983,7 @@
       },
       "source": [
         "# Reproduce\n",
-        "for x in 'yolov5s', 'yolov5m', 'yolov5l', 'yolov5x':\n",
+        "for x in 'yolov5n', 'yolov5s', 'yolov5m', 'yolov5l', 'yolov5x':\n",
         "  !python val.py --weights {x}.pt --data coco.yaml --img 640 --task speed  # speed\n",
         "  !python val.py --weights {x}.pt --data coco.yaml --img 640 --conf 0.001 --iou 0.65  # mAP"
       ],