Bump sphinx-autobuild from 2021.3.14 to 2024.9.19

Bumps [sphinx-autobuild](https://github.com/sphinx-doc/sphinx-autobuild) from 2021.3.14 to 2024.9.19.
- [Release notes](https://github.com/sphinx-doc/sphinx-autobuild/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx-autobuild/blob/main/NEWS.rst)
- [Commits](sphinx-doc/sphinx-autobuild@2021.03.14...2024.09.19)

---
updated-dependencies:
- dependency-name: sphinx-autobuild
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

pyproject.toml

@@ -135,7 +135,7 @@ develop = [
 docs = [
   "furo",
   "myst-parser[linkify]>=0.18,<5",
-  "sphinx-autobuild==2021.3.14", # Newer versions stopped "watching" appropriately?
+  "sphinx-autobuild==2024.9.19", # Newer versions stopped "watching" appropriately?
   "sphinx-copybutton",
   "sphinx-design-elements<1",
   "sphinxcontrib-mermaid<1",