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

[Paul Kirth via llvm-commits]

ilovepi wrote:

Also, this is related to this RFC: https://discourse.llvm.org/t/rfc-enabling-the-lit-internal-shell-by-default/80179

Removing `|&` was specifically called out by other contributors to be replaced. @connieyzhu I'd suggest mentioning that in the commit message.

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