regcomp.c: Remove no longer useful code

regcomp.c: Remove no longer useful code

This code has been obsoleted by the previous commit.  That commit looks
at a bracketed character class in general and optimizes it to some
faster and/or simpler operation if possible.  The code being removed in
this commit was originally added to try to find some optimizations that
were feasible to find in the sizing pass.  Now that we don't have a
sizing pass, and we find optimizations generally, this code doesn't add
any value.