fix: ignore pgoutput Type messages

[fengjikui]

Description

Postgres pgoutput can emit Y Type messages when custom types are present in the publication stream. MessageConsumer currently treats any unrecognized op as fatal, so a Type message raises ValueError: Unknown replication op 89 even though it does not contain row changes.

This PR makes MessageConsumer ignore op 89 / Y and adds a small regression test for that no-op behavior.

Addresses dlt-hub/dlt#4102.

Validation

• uv run pytest tests/pg_replication/test_pg_replication.py::test_message_consumer_ignores_type_message -q
• uv run black --check sources/pg_replication/helpers.py tests/pg_replication/test_pg_replication.py
• uv run flake8 --extend-ignore=W503 sources/pg_replication/helpers.py tests/pg_replication/test_pg_replication.py

Note: plain uv run flake8 sources/pg_replication/helpers.py tests/pg_replication/test_pg_replication.py still reports pre-existing W503 line-break warnings in unchanged lines; no new lint issues are introduced by this patch.

[roberto-palloni]

Hello! Do you have an estimate on how long would it take to merge and in which version it will be available? Thanks

[fengjikui]

I do not have a maintainer-side ETA for merge or release version. From the author side, the PR is mergeable and has an approval; the remaining workflow checks visible to me are skipped because this is a fork PR, so the next step depends on maintainer-side review/CI/merge handling.