Fix warnings from tests

Author: ai

test/plugins/blue.js

@@ -1,5 +1,5 @@
 module.exports = function (css) {
-    css.eachDecl(function (decl) {
+    css.walkDecls(function (decl) {
         if ( decl.value === 'black' ) decl.value = 'blue';
     });
 };

test/plugins/red.js

@@ -7,7 +7,7 @@ module.exports = {
             warning = true;
         }
 
-        css.eachDecl(function (decl) {
+        css.walkDecls(function (decl) {
             if ( decl.value === 'blue' ) decl.value = 'red';
         });
     }