[libunwind] [libunwind] Fix an inconsistent indentation (NFC) (PR #72314)

[Heejin Ahn via cfe-commits]

aheejin wrote:

> Making it consistent is good, but it sounds like we should update the .clang-format config file or reformat this whole file to not be indented.

I'm not sure what the clang-format policy for libunwind is. How about landing this as is and updating `.clang-format` or excluding this file as a follow-up, if libunwind maintainers think that's necessary? 

https://github.com/llvm/llvm-project/pull/72314