Base: Set TitleButtonsIconOnly for Cupertino theme

Author: https://github.com/MacDue
Commit: https://github.com/SerenityOS/serenity/commit/c80815fbb9
Pull-request: https://github.com/SerenityOS/serenity/pull/13782
Reviewed-by: https://github.com/linusg

Base/res/themes/Cupertino.ini

@@ -75,6 +75,7 @@ TitleAlignment=Center
 
 [Flags]
 IsDark=true
+TitleButtonsIconOnly=true
 
 [Metrics]
 BorderRadius=8