remove unused

packages/tree/src/tree.vue

@@ -14,7 +14,7 @@
   </div>
 </template>
 
-<script type="text/ecmascript-6">
+<script>
   import TreeStore from './model/tree-store';
   import {t} from 'element-ui/src/locale';
   import emitter from 'element-ui/src/mixins/emitter';