Update val.py `pad = 0.0 if task == speed else 0.5` (#5121)

* Update val.py `pad = 0.0 if task == speed else 0.5`

* Cleanup

val.py

@@ -147,8 +147,9 @@ def run(data,
     if not training:
         if device.type != 'cpu':
             model(torch.zeros(1, 3, imgsz, imgsz).to(device).type_as(next(model.parameters())))  # run once
+        pad = 0.0 if task == 'speed' else 0.5
         task = task if task in ('train', 'val', 'test') else 'val'  # path to train/val/test images
-        dataloader = create_dataloader(data[task], imgsz, batch_size, gs, single_cls, pad=0.5, rect=True,
+        dataloader = create_dataloader(data[task], imgsz, batch_size, gs, single_cls, pad=pad, rect=True,
                                        prefix=colorstr(f'{task}: '))[0]
 
     seen = 0