Remove banner from instructor dashboard

@shnayder @explorerleslie - as we discussed last week, this is to remove the banner from the instructor dashboard based on Renzo's metrics that not many are switching back to the legacy instructor dash.

![screen shot 2014-08-10 at 1 07 35 am](https://cloud.githubusercontent.com/assets/1985317/3868539/481bf8ce-204c-11e4-843a-3d2b53c4f3d7.png)