remover o filterwarnings do BlockingPortal quando starlette lancar versao com Kludex/starlette#3498 (verificar com python -W error::DeprecationWarning -c "import starlette.testclient") #1915

Context

Follow-up to #1871 Option A: pyproject.toml [tool.pytest.ini_options].filterwarnings (and the matching per-item mark in tests/conftest.py) ignores:

The anyio.abc.BlockingPortal alias is deprecated

so Dependabot uv-minor-patch can keep CI with addopts = -W error / pytest -v -W error.

Upstream: Kludex/starlette#3498 (stop using anyio.abc.BlockingPortal).

When to close

1. Starlette ships a release that includes that fix.
2. Confirm locally / in CI:

python -W error::DeprecationWarning -c "import starlette.testclient"

3. Remove the filterwarnings entry and the tests/conftest.py _BLOCKINGPORTAL_DEPRECATION_FILTER mark (keep addopts = -v -W error).
4. Re-run ./scripts/quick-test.sh --path tests/test_pytest_blockingportal_filterwarnings.py and drop that test file if the filter is gone.

Do not replace this with ignore::DeprecationWarning or a :anyio.abc module-scope filter.