[llvm] [PowerPC] clean unused PPC target feature FeatureBPERMD (PR #159782)

[Sergei Barannikov via llvm-commits]

s-barannikov wrote:

> They're definitely showing up as red for me at the time of merge.

That was before the merge commit, it seems. Merge commit didn't seem to re-trigger the failing jobs:

<img width="1348" height="504" alt="image" src="https://github.com/user-attachments/assets/2d91f7e7-c3af-4f4b-96ab-09082dfce09c" />


https://github.com/llvm/llvm-project/pull/159782