build(deps): bump certifi in /docs in the production-dependencies group

Bumps the production-dependencies group in /docs with 1 update: [certifi](https://github.com/certifi/python-certifi).


Updates `certifi` from 2026.5.20 to 2026.6.17
- [Commits](certifi/python-certifi@2026.05.20...2026.06.17)

---
updated-dependencies:
- dependency-name: certifi
  dependency-version: 2026.6.17
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: production-dependencies
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -3,7 +3,7 @@ Jinja2==3.1.6
 MarkupSafe==3.0.3
 Pygments==2.20.0
 Sphinx==8.2.3
-certifi==2026.5.20
+certifi==2026.6.17
 chardet==7.4.3
 commonmark==0.9.2
 docutils==0.20.1