[2.3] - Fix "treestate_id"

Sorry, i forgot to add this fix for #11476 (don't ask me why `treestate_id` is used in [`MODx.tree.Tree`](https://github.com/modxcms/revolution/blob/develop/manager/assets/modext/widgets/core/tree/modx.tree.js#L200) instead of default [`stateId`](http://docs.sencha.com/extjs/3.4.0/#!/api/Ext.Component-cfg-stateId))