Revert `torch.hub.load()` test (#4986)

Temporarily reverts https://github.com/ultralytics/yolov5/pull/4978 until torch 1.10 is released, which should resolve `urllib.error.HTTPError: HTTP Error 403: rate limit exceeded` errors generated by torch hub from GitHub actions runners.

.github/workflows/ci-testing.yml

@@ -83,7 +83,8 @@ jobs:
           # Python
           python - <<EOF
           import torch
-          model = torch.hub.load('ultralytics/yolov5', 'custom', path='runs/train/exp/weights/last.pt')
+          # Known issue, urllib.error.HTTPError: HTTP Error 403: rate limit exceeded, will be resolved in torch==1.10.0 
+          # model = torch.hub.load('ultralytics/yolov5', 'custom', path='runs/train/exp/weights/last.pt')
           EOF
 
         shell: bash