Removes classes for icons that are no longer included with Fabric.
Removes classes for icons that are no longer included with Fabric.

zkoehne/Office-UI-Fabric,OfficeDev/Office-UI-Fabric,OfficeDev/Office-UI-Fabric,zkoehne/Office-UI-Fabric,waldekmastykarz/Office-UI-Fabric,waldekmastykarz/Office-UI-Fabric