*/README: Update compatibility info of modules still using legacy is_admin API mod_admin_message mod_admin_probe mod_block_outgoing mod_broadcast mod_data_access mod_muc_config_restrict mod_muc_restrict_rooms

This module blocks configured queries that change server state.

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

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