[llvm] [NFC][bolt][test] Change '|&' to '2>&1 |' for lit internal shell support (PR #102402)

[Paul Kirth via llvm-commits]

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

LGTM, but let's have a BOLT maintainer weigh in just to be safe. This is the only occurrence of `|&`, so it should be safe to replace w/ the spelling we use in the rest of the project. 

https://github.com/llvm/llvm-project/pull/102402