[llvm] [VPlan] Change parent of VPReductionRecipe to VPRecipeWithIRFlags. NFC (PR #130881)

[Florian Hahn via llvm-commits]

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

LGTM, thanks!

For the title, something like `[VPlan] Make VPReductionRecipe a VPRecipeWithIRFlags. (NFC)` may be slightly more compact

https://github.com/llvm/llvm-project/pull/130881