chore(deps): 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@2024.02.04...2025.08.25)

---
updated-dependencies:
- dependency-name: sphinx-autobuild
  dependency-version: 2025.8.25
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements/documentation.txt

@@ -2,6 +2,6 @@
 # -----------------------
 
 myst-parser[linkify]>=2
-sphinx-autobuild>=2024
+sphinx-autobuild>=2025.8.25
 sphinx-copybutton>=0.5,<1
 sphinx-rtd-theme>=2