[clang] [clang][docs] Fix example in likely/unlikely attr documentation (PR #126372)

[via cfe-commits]

https://github.com/Sirraide commented:

Hmm, I think what this section is trying to demonstrate is that ‘*According to the standard*, this is in the path of execution and therefore *supposed* to be considered unlikely, but we don’t do that’, so maybe it’d be better to reword/expand the comment instead?

https://github.com/llvm/llvm-project/pull/126372