bug: google-cloud-ces fails mypy-3-14 due to unannotated header_params = {} in BidiRunSession

[quirogas]

During SDK regeneration via librarian generate, google-cloud-ces (SessionService. BidiRunSession) fails static type checking in CI (nox -s mypy-3-14).

Affected Files

- `google/cloud/ces_v1/services/session_service/client.py:1144`
- `google/cloud/ces_v1/services/session_service/async_client.py:649`
- `google/cloud/ces_v1beta/services/session_service/client.py:1144`
- `google/cloud/ces_v1beta/services/session_service/async_client.py:649`