graphics/krita: update to 5.2.6, latest upstream

There are release notes at
https://krita.org/en/posts/2024/krita-5-2-3-released/
https://krita.org/en/posts/2024/krita-5-2-5-released/
https://krita.org/en/posts/2024/krita-5-2-6-released/

5.2.6 is a hotfix for 5.2.5.