fixup: missing dependeny groups

Author: RonnyPfannschmidt

tox.ini

@@ -9,7 +9,7 @@ commands=
 setenv=
   _PYTEST_SETUP_SKIP_PLUGGY_DEP=1
   coverage: _PLUGGY_TOX_CMD=coverage run -m pytest
-extras=testing
+dependency_groups=testing
 deps=
   coverage: coverage
   pytestmain: git+https://github.com/pytest-dev/pytest.git@main