krita: 5.1.4 -> 5.1.5

https://krita.org/en/item/krita-5-1-5-released/
This fixes build after libraw update
(the announcement doesn't mention that).

pkgs/applications/graphics/krita/default.nix

···
 { callPackage, ... } @ args:
 
 callPackage ./generic.nix (args // {
-  version = "5.1.4";
+  version = "5.1.5";
   kde-channel = "stable";
-  sha256 = "sha256-wisCCGJZbrL92RHhsXnbvOewgb4RFFei6sr2rhzKLcs=";
+  sha256 = "1lx4x4affkbh47b7w5qvahkkr4db0vcw6h24nykak6gpy2z5wxqw";
 })