Tag cleanup -- no_legs -> cropped_legs

The wiki for no_legs seems to be outdated; if anything the tag should be used for either amputees, or ghosts which are purposely drawn without legs.

Cropped_legs currently has no wiki, but seems more suited for legs which are just cut-off because of how the artist has framed the image.

Ghosts have the ghost_tail tag, which works better than no_legs. It's just how we wouldn't use no_legs for mermaids or lamia.
amputee could benefit from additional information as to what is amputated, although I'd use tags like amputated_* (arm, arms, leg, legs, tail?, wings?, other appendages) for it instead.

The similar no_arms tag is also used for characters who naturally do not have arms. post #1359100