fix(material/theming): remove shadow css variable

Author: wagnermaciel

src/material/core/tokens/_m3-tokens.scss

@@ -1030,6 +1030,10 @@
 }
 
 @function _get-sys-color($type, $use-sys-vars, $ref) {
+  $mdc-sys-color: if($type == dark,
+    mdc-tokens.md-sys-color-values-dark($ref),
+    mdc-tokens.md-sys-color-values-light($ref));
+
   @if $use-sys-vars {
     @return (
       'background': var(--sys-background),
@@ -1066,7 +1070,7 @@
       'secondary-container': var(--sys-secondary-container),
       'secondary-fixed': var(--sys-secondary-fixed),
       'secondary-fixed-dim': var(--sys-secondary-fixed-dim),
-      'shadow': var(--sys-shadow),
+      'shadow': map.get($mdc-sys-color, shadow),
       'surface': var(--sys-surface),
       'surface-bright': var(--sys-surface-bright),
       'surface-container': var(--sys-surface-container),
@@ -1084,9 +1088,7 @@
     );
   }
 
-  @return if($type == dark,
-    mdc-tokens.md-sys-color-values-dark($ref),
-    mdc-tokens.md-sys-color-values-light($ref));
+  @return $mdc-sys-color;
 }
 
 @function _get-sys-typeface($use-sys-vars, $ref) {