[llvm] [llvm] remove incorrect `LLVM_ABI` annotation usage (PR #144606)

[Andrew Rogers via llvm-commits]

andrurogerz wrote:

@compnerd, @vgvassilev here's the first PR I've had to make to fix mistaken `LLVM_ABI` annotations by others. I think we will need to update to `ids` so that it catches this sort of mistake. Right now, `ids` focuses on on where annotations are missing, but to fully prevent Windows DLL build breaks, it will also need to flag annotations that are unnecessary or in the wrong place.

https://github.com/llvm/llvm-project/pull/144606