Presenting Foot utility alias

BUR #57261 has been approved by @nonamethanks.

create alias presenting_feet -> presenting_foot

Not sure which one is better, but there should be an alias in one direction or another. I typed "presenting_feet" on a recent post and was surprised it wasn't a tag.

We could keep presenting feet as the main tag and make presenting single foot and presenting both feet if you think that's something we need. We also have foot pussy which is not implied to anything.

The bulk update request #57261 (forum #427565) has been approved by @nonamethanks.