Fixed german copy permission translation.

Follow up to https://github.com/4teamwork/ftw.permissionmanager/pull/24.
Forgot to fix upper-case `Ü`.

![screen shot 2014-11-04 at 11 46 33](https://cloud.githubusercontent.com/assets/1375745/4898420/52f40892-6410-11e4-9b37-2ff392d496d2.png)


@maethu