refactor(material/core): remove touch target mixin

Removes the `if-touch-targets-supported` mixin since it isn't used anymore.

Author: crisbeto

src/material/_index.scss

@@ -146,9 +146,8 @@
 // MDC Helpers
 @forward './core/mdc-helpers/mdc-helpers' as private-* show
   private-disable-mdc-fallback-declarations, private-typography-config-level-from-mdc,
-  private-if-touch-targets-unsupported, $private-mdc-base-styles-query,
-  $private-mdc-base-styles-without-animation-query, $private-mdc-theme-styles-query,
-  $private-mdc-typography-styles-query;
+  $private-mdc-base-styles-query, $private-mdc-base-styles-without-animation-query,
+  $private-mdc-theme-styles-query, $private-mdc-typography-styles-query;
 
 // New theming APIs:
 @forward './core/theming/inspection' show get-theme-version, get-theme-type, get-theme-color,

src/material/core/mdc-helpers/_mdc-helpers.scss

@@ -5,7 +5,6 @@
 @use '@material/typography' as mdc-typography;
 @use '@material/theme/theme-color' as mdc-theme-color;
 @use '@material/theme/css' as mdc-theme-css;
-@use 'sass:meta';
 
 // A set of standard queries to use with MDC's queryable mixins.
 $mdc-base-styles-query: mdc-feature-targeting.without(mdc-feature-targeting.any(color, typography));
@@ -59,10 +58,3 @@ $mdc-typography-styles-query: typography;
   @content;
   mdc-theme-css.$enable-fallback-declarations: $previous-value;
 }
-
-// Excludes the passed-in CSS content if the layout is too dense to supports touch targets.
-@mixin if-touch-targets-unsupported($scale) {
-  @if ($scale == 'minimum' or (meta.type-of($scale) == 'number' and $scale < -1)) {
-    @content;
-  }
-}