Accept any Iterable for service_names

[dimo414]

Description of change

Passing a set works for me locally, but then Mypy gets mad because of this type hint.

Checklist:

• [ ] I have verified my MRE is sufficient to demonstrate the issue and solution by attempting to execute it myself
  • [x] OR I believe my contribution is minor enough that a typing test is sufficient.
• [ ] I have added tests to typesafety/test_grpc.yml for all APIs added or changed by this PR
• [ ] I have removed any code generation notices from anything seeded using mypy-protobuf.