[clang] [StaticAnalyzer] Fix state update in VisitObjCForCollectionStmt (PR #124477)

[Balazs Benics via cfe-commits]

steakhal wrote:

> I wish I could see your reply earlier! It took me a while to reduce the downstream reproducer and come up a minimal test. This way of testing looks great. Maybe I should add this test anyway. Thank you steakhal!

I think I'd still prefer the unittest over a lit test because its way less fragile.

https://github.com/llvm/llvm-project/pull/124477