qt6.qtdoc: clean up

pkgs/development/libraries/qt-6/modules/qtdoc.nix

@@ -16,12 +16,7 @@ qtModule {
   '';
   nativeBuildInputs = [ (qttools.override { withClang = true; }) ];
   propagatedBuildInputs = [ qtdeclarative ];
-  cmakeFlags = [
-    "-DCMAKE_MESSAGE_LOG_LEVEL=STATUS"
-  ];
-  dontUseNinjaBuild = true;
-  buildFlags = [ "docs" ];
-  dontUseNinjaInstall = true;
-  installFlags = [ "install_docs" ];
-  outputs = [ "out" ];
+
+  ninjaFlags = [ "docs" ];
+  installTargets = [ "install_docs" ];
 }