Removes the local re-import of api.streaming._session_payload_with_full_messages
inside test_in_tail_duplicate_guard_refuses_bounded_and_full_revision_accepted;
it is already imported at module level (line 17) and unused in the function body,
tripping F401 on CI's hosted lint. Mechanical maintainer fix per auto-fix policy.
Co-authored-by: webtecnica <webtecnica@users.noreply.github.com>