Always “config changed ('nb_render_image_options')”

[flying-sheep]

Describe the bug

context
When I run sphinx, it always invalidates the config.

I assume that’s because of a bug that (I introdoced and that) would be fixed in #599

expectation
I expected Sphinx’ cache to work

bug
But instead Sphinx never realizes that nb_render_image_options is unchanges

updating environment: [config changed ('nb_render_image_options')] 359 added, 0 changed, 0 removed

problem
This is a problem because local builds should be fast

Reproduce the bug

Build documentation with width/height metadata for an image and myst-nb

List your environment

myst-nb==1.1.0

[flying-sheep]

Fixed by #609