Remove this test for now.

It is not reliable to depend on the output of llvm_unreachable. The original
change will have proper tests when llvm-ar moves to lib/Object (soon).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186043 91177308-0d34-0410-b5e6-96231b3b80d8