language-menu.html: load flag-icon-css locally (#2803)

pages/examples/language-menu.html

@@ -10,7 +10,7 @@
   <!-- Font Awesome -->
   <link rel="stylesheet" href="../../plugins/fontawesome-free/css/all.min.css">
   <!-- flag-icon-css -->
-  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/flag-icon-css/3.3.0/css/flag-icon.min.css">
+  <link rel="stylesheet" href="../../plugins/flag-icon-css/css/flag-icon.min.css">
   <!-- Theme style -->
   <link rel="stylesheet" href="../../dist/css/adminlte.min.css">
 </head>