libxml2: 2.13.6 -> 2.13.8

Fixes CVE-2025-32415 [1] and CVE-2025-32414 [2]

Release notes: https://gitlab.gnome.org/GNOME/libxml2/-/releases/v2.13.8

[1] https://gitlab.gnome.org/GNOME/libxml2/-/issues/890
[2] https://gitlab.gnome.org/GNOME/libxml2/-/issues/889

pkgs/development/libraries/libxml2/default.nix

···
 
 stdenv.mkDerivation (finalAttrs: {
   pname = "libxml2";
-  version = "2.13.6";
+  version = "2.13.8";
 
   outputs =
     [
···
 
   src = fetchurl {
     url = "mirror://gnome/sources/libxml2/${lib.versions.majorMinor finalAttrs.version}/libxml2-${finalAttrs.version}.tar.xz";
-    hash = "sha256-9FNIAwdSSWj3oE7GXmTyqDqCWXO80mCi52kb6CrnDJY=";
+    hash = "sha256-J3KUyzMRmrcbK8gfL0Rem8lDW4k60VuyzSsOhZoO6Eo=";
   };
 
   strictDeps = true;