Remove a bad test. The GEP has nothing to do with devirtualization, it
has to do with pointer manipulation. I'm not 100% certain what IR
dragonegg is generating, but if anyone is super attached to this test
case they should add it back with proper FileCheck-ing of the actual IR
relevant to devirtualization (the load of the function pointer from the
vtable).

I'm just nuking it for now to get the build bot green. I may take a look
at whether I can convince dragonegg to build so I can check what it
actually outputs, but no guarantee.