LibGUI+Applications: Use the new layout system in the settings screens

Author: https://github.com/frhun
Commit: https://github.com/SerenityOS/serenity/commit/a6ec2b9d0a
Pull-request: https://github.com/SerenityOS/serenity/pull/14261
Reviewed-by: https://github.com/AtkinsSJ ✅
Reviewed-by: https://github.com/MacDue
Reviewed-by: https://github.com/mjz19910

Userland/Applications/MouseSettings/Theme.gml

@@ -12,7 +12,7 @@
         }
 
         @GUI::Widget {
-            shrink_to_fit: true
+            preferred_height: "fit"
             layout: @GUI::HorizontalBoxLayout {
                 spacing: 8
             }