[llvm] [PPC][NFC] Remove duplicate processor feature from pwr9/10/11 and future (PR #137903)

[Jon Roelofs via llvm-commits]

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@@ -435,8 +435,7 @@ def ProcessorFeatures {
      FeatureP9Vector,
      FeaturePPCPreRASched,
      FeaturePPCPostRASched,
-     FeatureISA3_0,
-     FeaturePredictableSelectIsExpensive
+     FeatureISA3_0
----------------
jroelofs wrote:

Might be a bit of a bigger refactor than you're looking to do here, but the AArch64 backend is a much better model for this: ISA features, and Tune features are separated out into parallel lists.

https://github.com/llvm/llvm-project/pull/137903