Users: On the 'Add New User' screen, don't show the roles dropdown if the...

Users: On the 'Add New User' screen, don't show the roles dropdown if the current user can't promote other users.

Fixes #50345.
Built from https://develop.svn.wordpress.org/trunk@48042


git-svn-id: https://core.svn.wordpress.org/trunk@47809 1a063a9b-81f0-0310-95a4-ce76da25c4cd