hoon: retain face on type in +lose:ar (for ?#)

[Fang-]

?# wuthax was stripping faces in some type subtraction scenarios, which is unexpected and undesirable.

Excluding .skin doesn't necessarily mean we lose any of .ref's faces. The %base and %leaf cases were already retaining them, we now do so for the %cell case too.

Previously:

> =+  l=(gulf 0 5)
> ?<  ?#([one=@ two=@ rest=~] l)  l
[i=0 [i=1 t=[i=2 t=~[3 4 5]]]]

Now:

> =+  l=(gulf 0 5)
> ?<  ?#([one=@ two=@ rest=~] l)  l
[i=0 t=[i=1 t=[i=2 t=~[3 4 5]]]]