test: repair docs/conftest.py for modern pytest

from typing import ClassVar

import pytest

from _pytest._code.code import TerminalRepr

from _pytest.assertion.util import _diff_text

from py._code.code import TerminalRepr

def pytest_collect_file(path, parent):

def pytest_collect_file(file_path, parent):

    """Checks if the file is a rst file and creates an

    :class:`ExampleFile` instance."""

    if path.ext == '.py' and path.dirname.endswith('code'):

        return ExampleFile.from_parent(parent, path=pathlib.Path(path.strpath))

    if file_path.suffix == '.py' and file_path.parent.name == 'code':

        return ExampleFile.from_parent(parent, path=file_path)

    else:

        return None