Fix double escaping issue in User Permissions Editor->Save alert()

getFormattedString(), which uses nsTextFormatter::smprintf, escapes backslashes resulting in the literal display of "\n" in the alert window.

This commit addresses the issue in the same method used in [Open-ILS/xul/staff_client/server/serial/batch_receive.js](https://github.com/evergreen-library-system/Evergreen/blob/0483dc441e97873b48f8f72595cc577bc1ac9015/Open-ILS/xul/staff_client/server/serial/batch_receive.js#L19).

-a