feat(css): Update style components

Signed-off-by: Valentin Popov <info@valentineus.link>

_scss/components/_core.scss

@@ -1,11 +1,10 @@
-@import 'utilities/boxsizing';
 @import 'utilities/textsizeadjust';
 
 *,
 *::after,
 *::before {
-  @include box-sizing(border-box);
   @include text-size-adjust(100%);
+  box-sizing: border-box;
 }
 
 html {

_scss/utilities/_boxsizing.scss

@@ -1,15 +0,0 @@
-// Box Sizing
-//
-// The box-sizing property in CSS controls how the box model
-// is handled for the element it applies to.
-//
-// Values: content-box | border-box
-// Default: content-box
-//
-// https://www.w3.org/TR/css-ui-3/#box-sizing
-@mixin box-sizing($value: content-box) {
-  -webkit-box-sizing: $value;
-     -moz-box-sizing: $value;
-      -ms-box-sizing: $value;
-          box-sizing: $value;
-}