Update sphinx-autobuild requirement in /requirements

Updates the requirements on [sphinx-autobuild](https://github.com/sphinx-doc/sphinx-autobuild) to permit the latest version.
- [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...2024.02.04)

---
updated-dependencies:
- dependency-name: sphinx-autobuild
  dependency-type: direct:production
...

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

requirements/documentation.txt

@@ -2,6 +2,6 @@
 # -----------------------
 
 myst-parser[linkify]>=1,<3
-sphinx-autobuild==2021.*
+sphinx-autobuild==2024.*
 sphinx-copybutton>=0.2,<1
 sphinx-rtd-theme>=1,<3