qt6.qtbase: remove xmlstarlet dependency

`xmlstarlet` is only necessary to minify the mime ypes resources [1].
It is virtually unnecessary: the closure size reduction from minification
here is mostly useless compared to the cost of including xmlstarlet in the closure.

[1] https://github.com/qt/qtbase/blob/475c951d69a326e7aed0f18f525a155dd95a6a6b/src/corelib/QtCompressMimeDatabase.cmake#L8-L15

Co-authored-by: K900 <me@0upti.me>

pkgs/development/libraries/qt-6/modules/qtbase/default.nix

@@ -12,7 +12,6 @@
   which,
   cmake,
   ninja,
-  xmlstarlet,
   libproxy,
   xorg,
   zstd,
@@ -179,7 +178,6 @@ stdenv.mkDerivation rec {
     pkg-config
     which
     cmake
-    xmlstarlet
     ninja
   ] ++ lib.optionals stdenv.hostPlatform.isDarwin [ moveBuildTree ];