[clang] [clang-format] Fix short function merging with macro expansion (PR #204421)

[via cfe-commits]

r4nt wrote:

>From a design point of view, this should still be 3 lines in the non-expanded state, and I expect that merging should happen in the non-expanded state. Thus, my question is: why are those 3 lines in the non-expanded format pass?

https://github.com/llvm/llvm-project/pull/204421