build(deps): bump mkdocs-include-markdown-plugin from 4.0.4 to 6.0.0

Bumps [mkdocs-include-markdown-plugin](https://github.com/mondeja/mkdocs-include-markdown-plugin) from 4.0.4 to 6.0.0.
- [Release notes](https://github.com/mondeja/mkdocs-include-markdown-plugin/releases)
- [Commits](https://github.com/mondeja/mkdocs-include-markdown-plugin/compare/v4.0.4...v6.0.0)

---
updated-dependencies:
- dependency-name: mkdocs-include-markdown-plugin
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

docs/requirements.txt

@@ -5,5 +5,5 @@ mkdocs-macros-plugin==1.0.2
 mkdocs-material==9.1.21
 mkdocs-minify-plugin==0.7.1
 mkdocs-redirects==1.2.1
-mkdocs-include-markdown-plugin==4.0.4
+mkdocs-include-markdown-plugin==6.0.0
 mkdocs-markdownextradata-plugin==0.2.5