Bump mkdocs from 1.2.1 to 1.2.3 in /docs

Bumps [mkdocs](https://github.com/mkdocs/mkdocs) from 1.2.1 to 1.2.3.
- [Release notes](https://github.com/mkdocs/mkdocs/releases)
- [Commits](https://github.com/mkdocs/mkdocs/compare/1.2.1...1.2.3)

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

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

docs/requirements.txt

@@ -1,4 +1,4 @@
-mkdocs==1.2.1
+mkdocs==1.2.3
 mkdocs-autorefs
 mkdocs-material
 mkdocs-material-extensions