chore: remote isWeapp mixin (#9236)

* chore: remote isWeapp mixin

* fix: demo locale

docs/site/demo-locale.js

@@ -5,15 +5,6 @@ Locale.add({
   'en-US': enUS,
 });
 
-export const DemoLocaleMixin = {
-  computed: {
-    // flag for vant-weapp demos
-    isWeapp() {
-      return location.search.indexOf('weapp=1') !== -1;
-    },
-  },
-};
-
 // switch lang after routing
 if (window.vueRouter) {
   window.vueRouter.afterEach((to) => {

docs/site/entry.js

@@ -1,11 +1,8 @@
-import { DemoLocaleMixin } from './demo-locale';
+import './demo-locale';
 import Lazyload from '../../src/lazyload';
 
 const { app } = window;
 if (app) {
-  // helper for demo locales
-  app.mixin(DemoLocaleMixin);
-
   app.use(Lazyload, {
     lazyComponent: true,
   });