Modify the minimum capability to allow to view the New User Approve page in the admin.

Note: The New User Approve page in the admin will be going away in a future version of the plugin. Please use the default Users page to manage users.

/**
* Modify default capability to allow editors to use new user approve page
* $cap the capability
*/
function change_nua_cap( $cap ) {
    return 'manage_categories';
}
add_filter( 'new_user_approve_minimum_cap', 'change_nua_cap' );