Currently all the WebDriver tests fail (at least internally on macOS, and I _strongly_ suspect in open source GTK/WPE).

This is mostly with errors like:

Tests/WebDriver/py/tests/wpt/tests/element_click/user_prompts.py:122: in test_default
    check_user_prompt_closed_with_exception(dialog_type, retval)
Tests/WebDriver/py/tests/wpt/tests/element_click/user_prompts.py:36: in check_user_prompt_closed_with_exception
    session.url = inline("<input type=text>")
E   AttributeError: 'async_generator' object has no attribute 'url'

This is caused by upgrade pytest_asyncio to 0.20.3 in 258166@main. Per its changelog, https://github.com/pytest-dev/pytest-asyncio/blob/v0.20.3/CHANGELOG.rst, both 0.19 and 0.20 had breaking changes.

By comparison, the vendored upstream copy (https://github.com/web-platform-tests/wpt/tree/master/tools/third_party/pytest-asyncio) is currently at 0.14, and that also works with Python 3.11.

As a first move, which gets the internal WebDriver tests working, let's downgrade to 0.18.3.