locale.c: Fix dangling set of LC_NUMERIC to C

locale.c: Fix dangling set of LC_NUMERIC to C

In the past, we've kept LC_NUMERIC in the C locale, because so much code
relies on the radix character being a dot.  5.27.9 added an enhancement
that checks if the current locale already has it be a dot.  If so, it's
fine to keep the locale in that one.

The spot fixed by this commit didn't get updated to account for this
change.

(I realize that the docs also need to be updated; that will be in a
future commit)