[llvm] [Utils][vim] Match more hexadecimal float constants (PR #99000)

[Fraser Cormack via llvm-commits]

frasercrmck wrote:

> Thanks, LGTM!
> 
> I guess this intends to match https://llvm.org/docs/LangRef.html#simple-constants?

Yep, I'll link that in the commit message. Cheers!

https://github.com/llvm/llvm-project/pull/99000