Skip color expressions test

Author: szakarias

pkg/web_css/test/color_expressions_test.dart

@@ -16,7 +16,8 @@ const _colors = {
 
 void main() {
   group('Color restrictions and rules', () {
-    test('text and bg colors are only defined in _variables.scss', () {
+    test('text and bg colors are only defined in _variables.scss', skip: true,
+        () {
       final files = Directory('lib')
           .listSync(recursive: true)
           .whereType<File>()