Bump certifi from 2025.10.5 to 2026.1.4 in /docs

Bumps [certifi](https://github.com/certifi/python-certifi) from 2025.10.5 to 2026.1.4.
- [Commits](certifi/python-certifi@2025.10.05...2026.01.04)

---
updated-dependencies:
- dependency-name: certifi
  dependency-version: 2026.1.4
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -3,7 +3,7 @@ MarkupSafe==3.0.3
 Pygments==2.19.2
 alabaster==1.0.0
 babel==2.17.0
-certifi==2025.10.5
+certifi==2026.1.4
 chardet==5.2.0
 commonmark==0.9.1
 docutils==0.21.2