x11-themes/matcha-gtk-themes: update to 2025-04-11

While here:

• Remove gtk2 engines
• Remove post-patch target which is not needed anymore

Changelog:

• https://github.com/vinceliuice/Matcha-gtk-theme/releases/tag/2024-05-01
• https://github.com/vinceliuice/Matcha-gtk-theme/releases/tag/2025-04-11

PR: 289410
Reported by: Olivier Duchateau <duchateau.olivier@gmail.com>
Approved by: Alexander Vereeken <Alexander88207@protonmail.com> (maintainer)