[llvm] [LoopVectorize][NFC] Disable output for tests that don't need it (PR #124747)

[Florian Hahn via llvm-commits]

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

LGTM, thanks.

Presumably this may slightly speed up running some of the tests?

https://github.com/llvm/llvm-project/pull/124747