textproc/man2html: update to 3.1.20240105

Upstream changes:

• change the special case of bold italics to "-mixsecs" option. o allow a special case of bold italics (used in captoinfo.1m in ncurses) o provide a special case for ncurses's main manpage, which now uses italics for the subsections defining environment variables, rather than bold. o convert remaining tabs to spaces (perl tidy already did most).
  
  o reset variable used to splice links which are broken by hyphenation, if the bold text happens to not match the see-also pattern. This occurred with ncurses curs_refresh.3x.html file.
  
  o fix a case where optional pattern in substitution did not match, causing an uninitialized-variable warning.