chore(deps): bump mkdocs from 1.1.2 to 1.2.3 in /docs (#347)

Bumps [mkdocs](https://github.com/mkdocs/mkdocs) from 1.1.2 to 1.2.3.
- [Release notes](https://github.com/mkdocs/mkdocs/releases)
- [Commits](mkdocs/mkdocs@1.1.2...1.2.3)

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/requirements.txt

@@ -1,4 +1,4 @@
-mkdocs==1.1.2
+mkdocs==1.2.3
 mkdocs-material==7.1.7
 markdown_include==0.6.0
 pygments==2.7.4