fix(scss): remove use of math.div

Author: zwliew

website/src/views/settings/ThemeOption.scss

@@ -1,5 +1,3 @@
-@use "sass:math";
-
 @import '~styles/utils/modules-entry';
 
 $theme-selected-bg-color: var(--gray-lighter);
@@ -30,7 +28,7 @@ $theme-option-gap: 0.7rem;
   $number-colors: 8;
 
   .colorItem {
-    $size: math.div(100%, $number-colors);
+    $size: 12.5%; // 100% / $number-colors
 
     display: inline-block;
     width: $size;