[clang] [analyzer] Modernize FuchsiaHandleChecker (PR #111588)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

> I just saw it in various easy checkers like `ValistChecker`, so I thought it's "standard" way of reporting.

Yes, ValistChecker is another example where it's useless. By the way that's the first checker that I wrote (not completely alone) when I was an intern many years ago -- maybe when I'll have some free time I'll get rid of the visitor there.

https://github.com/llvm/llvm-project/pull/111588