Adw/PreferencesWindow: fix crash in Ephy (#1317)

Author: danirabbit

src/gtk-4.0/widgets/adw/PreferencesWindow.scss

@@ -7,9 +7,8 @@ window.preferences.csd {
         viewswitcher button.toggle {
             border-radius: rem(3px);
 
-            image {
-                opacity: 0;
-                -gtk-icon-size: 0;
+            box.horizontal {
+                border-spacing: 0.5em;
             }
         }
     }