graphics/krita: Update to 6.0.2.1 and switch to Qt6
Although the same tarball is used for 5.3.2.1 (Qt5) and 6.0.2.1 (Qt6),
Qt6 build is still considered experimental. Both versions are almost
functionally identical, with 6.0.x having more Wayland functionality.
Announcement: https://krita.org/en/posts/2026/krita-5.3.0-released/
https://krita.org/en/posts/2026/krita-5.3.1-released/ https://krita.org/en/posts/2026/krita-5.3.2-released/ https://krita.org/en/posts/2026/krita-5.3.2.1-released/