devdeps CI tests failing for ellipse and rectangle selectors

[larrybradley]

The devdeps CI tests are failing for ellipse and rectangle selections when invalid kwargs are input to as_mpl_selector:

https://github.com/astropy/regions/actions/runs/20730257507/job/59516157314

pytest.PytestUnraisableExceptionWarning: Exception ignored in: <function AxesWidget.__del__ at 0x7f7de45bec00>

This appears to be caused by matplotlib (dev), which introduced a new __del__ method to AxesWidget.

[larrybradley]

Possible fix: matplotlib/matplotlib#30935