[llvm] [LV] NFCI: Create VPExpressions in transformToPartialReductions. (PR #182863)

[Benjamin Maxwell via llvm-commits]

MacDue wrote:

> Good point. Let me know if you want me to remove that in this PR, or in a follow up.

Up to you. Either is fine as long as we don't leave around untested code :slightly_smiling_face:

https://github.com/llvm/llvm-project/pull/182863