build(deps): bump certifi from 2019.9.11 to 2023.7.22 in /docs

Bumps [certifi](https://github.com/certifi/python-certifi) from 2019.9.11 to 2023.7.22.
- [Commits](certifi/python-certifi@2019.09.11...2023.07.22)

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

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

docs/requirements.txt

@@ -1,6 +1,6 @@
 alabaster==0.7.12
 Babel==2.9.1
-certifi==2019.9.11
+certifi==2023.7.22
 chardet==3.0.4
 docutils==0.15.2
 idna==3.7