How did we lose the scipy dependency in building the docs?

Thanks @NelleV !

There seem to be a conflict, please backport manually

We "do" and we "don't"; e.g., these two examples use scipy:

• https://github.com/matplotlib/matplotlib/blob/a9a8634f17791f00e8c88c0b3d467e6be3c32c07/examples/animation/double_pendulum_animated_sgskip.py
• https://github.com/matplotlib/matplotlib/blob/81495363d283809021b5ae4fc87bbd5edbbb3f6c/examples/animation/bayes_update_sgskip.py

But they're currently being skipped.

They're both animations, so we "don't" until s-g starts supporting animations...

The changes to check_deps from #9365 did not get backported.

Re-milestoned this to 2.2 and not backporting, any protests?

I don't think this needs backporting.