x11-themes/wpgtk: update to 6.5.5

A patch release.

Upstream is at 6.5.7 already, but more recent versions have not been
uploaded to PYPI yet.

Changelog: https://github.com/deviantfero/wpgtk/compare/6.5.0...6.5.5

MFH: 2023Q2
(cherry picked from commit 616e412ad7cbab7a887441bbb7fde149b28e2951)