Remove deprecated img_size args in SwinUNETR (#416)

Remove deprecated `img_size` args in `SwinUNETR`
Add `allow_smaller=True` in CropForeground / CropForegroundd since
default value has been changed

Project-MONAI/MONAI#8430

---------

Signed-off-by: YunLiu <55491388+KumoLiu@users.noreply.github.com>

Author: KumoLiu

data/data_pretrain.py

@@ -21,7 +21,6 @@
     AsChannelFirstd,
     AsDiscrete,
     Compose,
-    CropForegroundd,
     LoadImaged,
     NormalizeIntensityd,
     Orientationd,