chore(deps): bump mkdocs-macros-plugin in /hack/api-docs (#5190)

Bumps [mkdocs-macros-plugin](https://github.com/fralau/mkdocs_macros_plugin) from 1.3.7 to 1.3.9.
- [Release notes](https://github.com/fralau/mkdocs_macros_plugin/releases)
- [Changelog](https://github.com/fralau/mkdocs-macros-plugin/blob/master/CHANGELOG.md)
- [Commits](https://github.com/fralau/mkdocs_macros_plugin/compare/v1.3.7...v1.3.9)

---
updated-dependencies:
- dependency-name: mkdocs-macros-plugin
  dependency-version: 1.3.9
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Moritz Johner <moolen@users.noreply.github.com>

hack/api-docs/requirements.txt

@@ -17,7 +17,7 @@ MarkupSafe==3.0.2
 mergedeep==1.3.4
 mike @ git+https://github.com/jimporter/mike@300593c338b18f61f604d18457c351e166318020
 mkdocs==1.6.1
-mkdocs-macros-plugin==1.3.7
+mkdocs-macros-plugin==1.3.9
 mkdocs-material==9.6.16
 mkdocs-material-extensions==1.3.1
 mkdocs-minify-plugin==0.8.0