[llvm] Fix typo in section name for STYP_EXCEPT (PR #161959)

[James Henderson via llvm-commits]

https://github.com/jh7370 commented:

Thanks, looks reasonable to me, but I'd like an XCOFF maintainer to sign off, so I've added a few who I know work in the area, as reviewers.

https://github.com/llvm/llvm-project/pull/161959