Make likelihood lit test less brittle

Jeremy Morse discovered an issue with the lit test introduced in D88363. The
test gives different results for Sony's `-O1`.

The test needs to run at `-O1` otherwise the likelihood attribute will be
ignored. Instead of running all `-O1` passes it only runs the lower-expect pass
which is needed to lower `__builtin_expect`.

Differential Revision: https://reviews.llvm.org/D89204