Remove bad debug info test.

This test case doesn't belong in Clang (it's testing IndVarSimplify) but
in an effort to reproduce the test case this was intended to cover (by
essentially reverting r134441) I wasn't able to reproduce the failure
this test case should've produced. So I haven't ported this down to
LLVM, instead I'm just deleting it.

I suspect the test is just underconstrained, but I've no great interest
in trying hard to fix it right now - if anyone else wants to, I'd be
more than welcome to that.