Use the new names for the swh.scheduler test fixtures

conftest.py

pytest.ini

requirements-test.txt

swh/lister/bitbucket/tests/test_tasks.py

swh/lister/cgit/tests/test_tasks.py

swh/lister/core/tests/conftest.py

swh/lister/cran/tests/test_tasks.py

swh/lister/debian/tests/test_tasks.py

swh/lister/gitea/tests/test_tasks.py

swh/lister/github/tests/test_tasks.py

swh/lister/gitlab/tests/test_tasks.py

swh/lister/gnu/tests/test_tasks.py

swh/lister/launchpad/tests/test_tasks.py

swh/lister/npm/tests/test_tasks.py

swh/lister/packagist/tests/test_tasks.py

swh/lister/phabricator/tests/test_tasks.py

swh/lister/pypi/tests/test_tasks.py

swh/lister/tests/test_cli.py

tox.ini