regcomp.c: Remove unreachable code

regcomp.c: Remove unreachable code

This code no longer gets executed, as the single multi-char fold in the
Latin1 range is pre-folded before this code sees it.  The surrounding
code didn't properly handle multi-char folds either.

Not having to deal with this allows us to not have to call the general
purpose function, but we do have to deal with one edge case