Bump mkdocs-minify-plugin from 0.6.2 to 0.6.4

Bumps [mkdocs-minify-plugin](https://github.com/byrnereese/mkdocs-minify-plugin) from 0.6.2 to 0.6.4.
- [Release notes](https://github.com/byrnereese/mkdocs-minify-plugin/releases)
- [Commits](https://github.com/byrnereese/mkdocs-minify-plugin/compare/0.6.2...0.6.4)

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

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

docs/requirements.txt

@@ -1,4 +1,4 @@
 mkdocs-awesome-pages-plugin==2.8.0
 mkdocs-material==9.1.2
-mkdocs-minify-plugin==0.6.2
+mkdocs-minify-plugin==0.6.4
 mkdocs-redirects==1.2.0