triangle_halo alias

BUR #55968 has been approved by @nonamethanks.

create alias triangular_halo -> triangle_halo

I have no opinion on what should be the primary name, but I sometimes tend to type "triangular" (i.e. adjective like rectangular) first before correcting myself, so I can imagine someone else doing the same and not knowing the actual tag name assume that it just doesn't exist.

We are a bit inconsistent here. We have a lot of triangle tags (triangle mouth) and a bunch of triangular tags (triangular headpiece).

The bulk update request #55968 (forum #422642) has been approved by @nonamethanks.