Bump certifi from 2015.11.20.1 to 2022.12.7 in /doc

Bumps [certifi](https://github.com/certifi/python-certifi) from 2015.11.20.1 to 2022.12.7.
- [Release notes](https://github.com/certifi/python-certifi/releases)
- [Commits](https://github.com/certifi/python-certifi/compare/2015.11.20.1...2022.12.07)

---
updated-dependencies:
- dependency-name: certifi
  dependency-type: direct:production
...

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

doc/requirements.txt

@@ -3,7 +3,7 @@ argh==0.26.1
 Babel==2.2.0
 backports-abc==0.4
 backports.ssl-match-hostname==3.5.0.1
-certifi==2015.11.20.1
+certifi==2022.12.7
 CommonMark==0.5.4
 docutils==0.12
 Jinja2==2.8