[llvm] [analyzer] Add missing include <unordered_map> to llvm/lib/Support/Z3Solver.cpp (PR #106410)

[Luke Shingles via llvm-commits]

lukeshingles wrote:

@NagyDonat since you reviewed [#97265](https://github.com/llvm/llvm-project/pull/97265), maybe you can review this fix?

https://github.com/llvm/llvm-project/pull/106410