[DebugInfo] Fix typo "DWARG" in test comment (NFC)

Summary:
The correct spelling is "DWARF", the debugging format, not "DWARG".
The typo is in a (not executed by lit) comment in a test file, so
fixing it does not result in any functional change.

Test Plan: check-llvm, just in case



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332878 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed