regexprops-generic: update from regex.h

regexprops-generic: update from regex.h

* doc/regexprops-generic.texi: Re-generate by running the 'regexprops'
binary from GNU findutils:
  ./regexprops "Regular Expressions" generic
At least the recent(ish) change (efd5c380ff) to regex.h aligning
gnulib with Emacs behavior had made this document out-of-date.
Reported by Collin Funk in
<https://lists.gnu.org/archive/html/bug-gnulib/2025-07/msg00037.html>.
Additionally, today's findutils commit c9c2c51175 fixed the sort order
of the Texinfo nodes.