Removing its display won't remove its functionality. Also removing its display will make it very difficult to manage users in the group. At any rate it's rendered in and can be removed from the below template file.
components/com_comprofiler/plugin/user/plug_cbgroupjive/templates/default/group_users.php
You'll see an API call to getDropdown, which you can basically just remove and that'll get rid of the menu display.