It's been discontinued. The options are IIS Express or IIS. And that's for the full range of the product, not just a VS Express thing.
I can't find a specific posting about it, but in e.g. Accessing the ASP.NET Web Configuration Tool in Visual Studio 2013, it starts with:
As many of you have noticed, the option to select “ASP.Net Web Configuration Manager” is no longer in Visual Studio 2013 Preview. This is due to the removal of the Visual Studio Development Server (or Cassini) from the product. However, ...
(My emphasis)