Code Quality: Simplify user permission check for importing new users.

This removes a redundant conditional in the `check_import_new_users()` function, simplifying its logic to directly return the result of the permission check.

Follow-up to [https://mu.trac.wordpress.org/changeset/1829 mu:1829], [39945].

Props Soean.
See #64238.

git-svn-id: https://develop.svn.wordpress.org/trunk@62086 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-admin/includes/ms.php

@@ -614,11 +614,7 @@ 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 ( ! current_user_can( 'manage_network_users' ) ) {
-		return false;
-	}
-
-	return true;
+	return current_user_can( 'manage_network_users' );
 }
 // See "import_allow_fetch_attachments" and "import_attachment_size_limit" filters too.