[clang] [clang][dataflow] Disambiguate a ref to "internal" in CachedConstAccessorsLattice (PR #113601)

[Nico Weber via cfe-commits]

nico wrote:

I think this'll fix the build, thanks!

However, the root cause is probably that the `AST_MATCHER_P_OVERLOAD` instantiation in clang/lib/Analysis/FlowSensitive/Models/UncheckedOptionalAccessModel.cpp is in an unnamed namespace that's inside namespace `clang::dataflow`, right? Should we move that to just an unnamed namespace at the top of that file that isn't in clang::dataflow?

https://github.com/llvm/llvm-project/pull/113601