erratic result from colorscale validator test

The test `tests/test_plotly_utils/validators/test_colorscale_validator.py::test_acceptance_named[Inferno_r]` fails when the entire test suite is run with `pytest tests` in the `codegen2` branch (PR #4978) but succeeds when `pytest tests/test_plotly_utils/validators/test_colorscale_validator.py` is run on its own. (Testing done with Python 3.11.9.)