I have the delete shortcut ready for shader effects like the other stack UIs,
but because they're missing an update notification it doesn't work properly.
Theoretically this should be done whenever a context for the properties editor
is added.
The main thing I wanted to check on is whether I added `ND_SHADERFX` in the correct place.
But also, @antoniov. I checked viewport cycles and EEVEE rendering and it all works, so I'm
assuming I have the update in all the necessary places.