[2.3] Manager Theme: ComboBox Pagination Fix

This PR is a proposal for fixing #11713

currently it looks and feels like that:
![modx mgrtheme combobox-pagination new](https://cloud.githubusercontent.com/assets/445501/3608580/98b0c680-0d63-11e4-83ee-8db2d62670c3.gif)

there is that "Page" text, I thought it's not really necessary, but I'm not sure about it and would love to hear your opinion on this, with the "Page" Text it could look like this:
![bildschirmfoto 2014-07-17 um 05 33 29](https://cloud.githubusercontent.com/assets/445501/3608587/b5ca980e-0d63-11e4-8ef9-6eda7180d576.png)