Varia: move font-family mixin to proper place

varia/sass/abstracts/_mixins.scss

@@ -91,3 +91,12 @@
 		margin-top: -($offset-bottom);
 	}
 }
+
+/**
+ * Add font-family using CSS variables.
+ * It also adds the proper fallback for browsers without support.
+ */
+@mixin font-family( $config_map ) {
+	font-family: #{map-deep-get( $config_map, 'fallback' )}; // For browsers without CSS custom properties support.
+	font-family: var( #{map-deep-get( $config_map, 'css-var')}, #{map-deep-get( $config_map, 'fallback' )} );
+}

varia/sass/base/legacy/_mixins-master.scss

@@ -119,8 +119,3 @@
 @mixin font-family-old( $font_family: $font__body ) {
 	font-family: $font_family;
 }
-
-@mixin font-family( $config_map ) {
-	font-family: #{map-deep-get( $config_map, 'fallback' )}; // For browsers without CSS custom properties support.
-	font-family: var( #{map-deep-get( $config_map, 'css-var')}, #{map-deep-get( $config_map, 'fallback' )} );
-}