Switch from GabrielBB/xvfb-action to aganders3/headless-gui

[Czaki]

Following main repository https://github.com/napari/napari/pull/5478

[imagesc-bot]

This pull request has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/request-for-update-of-gui-tests-gihub-workflows-for-napari-plugins/76196/1