`build_docs.yml` bloats size of scikit-image/docs with regular commits to ~1 GiB about scikit-image HOT 2 OPEN

We've been rewriting history to remove the old commits with each release and periodically delete older history. For example, here is what the repo looked like when we released 0.22:

* 2342e18b0 - (HEAD -> gh-pages, origin/gh-pages) Add 0.22.x (9 weeks ago) [Jarrod Millman]
* 04503d6ba - Add 0.21.x (6 months ago) [Jarrod Millman]
* 26f1b7b52 - Update stable to point to 0.20.x (6 months ago) [Stefan van der Walt]
* 82d2924ef - Updated doc release: 0.20.x (6 months ago) [Stefan van der Walt]
* d6f97aab9 - All doc builds up to 0.19.x (1 year, 3 months ago) [Stefan van der Walt]

When we make the next release there will only be one additional commit.

It seems to work fine. Normally, the only time you need to download things is during the release process and only the release manager needs to do it. So I am not sure this is much of an issue.

from scikit-image.

The reason this may become an issue now, is that we are going to start including a pyodide build of the library, so that's on the order of tens of megabytes extra per commit.

I think amending an existing dev commit is totally safe, and easy to implement.

from scikit-image.