Simplify val.py benchmark mode with speed mode (#9674)

Update

val.py

@@ -169,8 +169,7 @@ def run(
             assert ncm == nc, f'{weights} ({ncm} classes) trained on different --data than what you passed ({nc} ' \
                               f'classes). Pass correct combination of --weights and --data that are trained together.'
         model.warmup(imgsz=(1 if pt else batch_size, 3, imgsz, imgsz))  # warmup
-        pad = 0.0 if task in ('speed', 'benchmark') else 0.5
-        rect = False if task == 'benchmark' else pt  # square inference for benchmarks
+        pad, rect = (0.0, False) if task == 'speed' else (0.5, pt)  # square inference for benchmarks
         task = task if task in ('train', 'val', 'test') else 'val'  # path to train/val/test images
         dataloader = create_dataloader(data[task],
                                        imgsz,