removing obsolete separator line

as mentioned by @Smanzi in Pull Request https://github.com/joomla/joomla-cms/pull/5199 there are two separator lines right after each other. (https://cloud.githubusercontent.com/assets/4165717/5205697/c6c40ebc-7599-11e4-99ec-6150c632c358.PNG)
One of them is obsolete. This pull request removes the second separator line.