[clang] [Sema] Fix c23 not checking CheckBoolLikeConversion (PR #79588)

[Pil Eghoff via cfe-commits]

pileghoff wrote:

I can also see i broke the `n3042.c` test. Stuff like `if (null_val) {}` now throws a warning, since `null_val` is a constant.

I would expect this warning to be okay in that scenario?

https://github.com/llvm/llvm-project/pull/79588