Bump mkdocs from 1.4.1 to 1.4.2 in /docs

Bumps [mkdocs](https://github.com/mkdocs/mkdocs) from 1.4.1 to 1.4.2.
- [Release notes](https://github.com/mkdocs/mkdocs/releases)
- [Commits](mkdocs/mkdocs@1.4.1...1.4.2)

---
updated-dependencies:
- dependency-name: mkdocs
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

docs/requirements.txt

@@ -1,6 +1,6 @@
 jinja2==3.1.2
 markdown==3.3.7
-mkdocs==1.4.1
+mkdocs==1.4.2
 readthedocs-sphinx-search==0.1.2
 sphinx==5.3.0
 sphinx_rtd_theme==1.0.0