Discrepancy in capabilities for removing users on Multisite. #2742

Currently in the permissions check for deleting users we check for current_user_can( 'delete_user', $id ). We however only support removing users from a site at the moment, which actually uses a different capability remove_users. We would need to add a check for current_user_can( 'remove_user', $id ) for multisite installs. Support for deletion from the entire network is a separate issue in #1922, that is not necessarily related with this issue.