⬆️ Bump mkdocs-htmlproofer-plugin in /docs/mkdocs

Bumps [mkdocs-htmlproofer-plugin](https://github.com/manuzhang/mkdocs-htmlproofer-plugin) from 1.4.1 to 1.5.0.
- [Release notes](https://github.com/manuzhang/mkdocs-htmlproofer-plugin/releases)
- [Commits](https://github.com/manuzhang/mkdocs-htmlproofer-plugin/compare/v1.4.1...v1.5.0)

---
updated-dependencies:
- dependency-name: mkdocs-htmlproofer-plugin
  dependency-version: 1.5.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

docs/mkdocs/requirements.txt

@@ -6,6 +6,6 @@ mkdocs-material==9.7.1                             # theme for mkdocs
 mkdocs-material-extensions==1.3.1                   # extensions
 mkdocs-minify-plugin==0.8.0                         # plugin "minify"
 mkdocs-redirects==1.2.2                             # plugin "redirects"
-mkdocs-htmlproofer-plugin==1.4.1                    # plugin "htmlproofer"
+mkdocs-htmlproofer-plugin==1.5.0                    # plugin "htmlproofer"
 
 PyYAML==6.0.3                                       # linter