ENH: Swallow PySide6 warning #1511

Job	Run time
pytest matrix / ubuntu / MNE main	10m 22s
PyQt5 / ubuntu	3m 6s
pytest matrix / ubuntu / MNE maint/1.7	10m 13s
PyQt6 / ubuntu	10m 19s
pytest matrix / windows / MNE main	9m 47s
PySide6 / ubuntu	10m 19s
pytest matrix / windows / MNE maint/1.7	10m 8s
pytest matrix / macos / MNE main	4m 59s
PySide6 / macos	10m 23s
pytest matrix / macos / MNE maint/1.7	5m 10s
PySide6 / windows	10m 38s
pytest no opengl / ubuntu / MNE main	8m 42s
pytest no opengl / ubuntu / MNE maint/1.7	8m 34s
pytest old / ubuntu / MNE maint/1.5	10m 18s
pytest pip-pre / ubuntu / MNE main	10m 55s
	2h 13m 53s

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