alias cropped_feet -> cropped_legs

BUR #22585 has been approved by @nonamethanks.

create alias cropped_feet -> cropped_legs

In 2018, cropped feet was replaced with cropped legs. Five years later, the cropped feet tag started being added to posts again. A previous BUR (forum #137998) was made to create this same alias, but it was never approved.

This BUR is to help reinforce what seems to be the current status quo for these tags. There was clearly a reason for discontinuing the use of cropped feet, but I can't find any information about it. I don't know if we decided to bring cropped feet back or whether or not we should, so I'm hoping other users will be able to explain what's going on with these tags.

cropped feet needs to be cleaned first, because we also have feet out of frame. cropped feet/cropped legs is when the legs are partially drawn but cut off at the feet or before, while feet out of frame is for feet being out of frame. Compare post #7111249 vs post #6871112.

Okay, I think I got them all.

The bulk update request #22585 (forum #265789) has been approved by @nonamethanks.