Multisite: Replace `is_super_admin()` with `manage_network_users` when trying to import new users.

Props bhargavbhandari90.
Fixes #39212. See #37616.


git-svn-id: https://develop.svn.wordpress.org/trunk@39945 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/includes/ms.php

@@ -704,8 +704,10 @@ function _access_denied_splash() {
  * @return bool True if the user has proper permissions, false if they do not.
  */
 function check_import_new_users( $permission ) {
-	if ( !is_super_admin() )
+	if ( ! current_user_can( 'manage_network_users' ) ) {
 		return false;
+	}
+
 	return true;
 }
 // See "import_allow_fetch_attachments" and "import_attachment_size_limit" filters too.