MAINT: remove cell metadata `editable` and `slideshow` #439

Job	Run time
style / Determine skipped pre-commit hooks	6s
pytest / Determine job matrix	4s
doc / nb / Execute and build documentation	2m 16s
doc / linkcheck / Check external links	38s
pytest / Run unit tests (3.10, ubuntu-22.04)	1m 19s
pytest / Run unit tests (3.11, ubuntu-22.04)	1m 10s
pytest / Run unit tests (3.12, ubuntu-22.04)	1m 21s
pytest / Run unit tests (3.7, ubuntu-22.04)	1m 42s
pytest / Run unit tests (3.8, ubuntu-22.04)	1m 30s
pytest / Run unit tests (3.9, ubuntu-22.04, qrules)	4m 36s
pytest / Run unit tests (3.9, macos-12)	2m 10s
style / Run local pre-commit hooks	44s
style / Run taplo through pre-commit	26s
style / Push changes	0s
doc / Upload to GitHub Pages	0s
	18m 2s

Provide feedback