*/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 lets you block connections to any remote servers not on a
whitelist.

``` {.lua}
s2s_whitelist = {
    "example.org",
}
```