DebugInfo: Generalize a test case to not depend on abbreviation numbering.

It's an unnecessary detail for this test and just gets in the way when
making unrelated changes to the output in this test.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209553 91177308-0d34-0410-b5e6-96231b3b80d8