Bump docutils from 0.20.1 to 0.21.2 in /docs

Bumps [docutils](https://docutils.sourceforge.io) from 0.20.1 to 0.21.2.

---
updated-dependencies:
- dependency-name: docutils
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

docs/requirements.txt

@@ -3,7 +3,7 @@
 myst-parser==2.0.0
 Sphinx==7.3.7
 # Older versions break Sphinx even though they're declared to be supported.
-docutils==0.20.1
+docutils==0.21.2
 sphinxcontrib-programoutput==0.17
 sphinx_copybutton==0.5.2
 furo==2024.1.29