mod_groups_muc_bookmarks: fix typo/leftover from refactor The update_bookmark function no longer takes a "current" argument; passing it causes havoc in service:publish (because it gets the room JID instaed of the item as item).

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```