[llvm-branch-commits] [clang] [llvm] [PowerPC] Update V18.1.0 release notes (PR #81631)

[Lei Huang via llvm-branch-commits]

https://github.com/lei137 approved this pull request.

Just some nits for spacing.  Otherwise LGTM
Thx

https://github.com/llvm/llvm-project/pull/81631