[llvm] [LV][NFC] Remove instcombine pass from RUN lines of simple tests (PR #196257)

[David Sherwood via llvm-commits]

david-arm wrote:

NOTE: I plan to look at removing instcombine from other tests as well, but the changes are greater in those cases. I'd like to first see if there are any useful optimisations we could do in vplan to reduce the estimated cost by mirroring the similar instcombine transform. If I do land some of these vplan simplifications first that would reduce any subsequent diffs.

https://github.com/llvm/llvm-project/pull/196257