chore(deps): bump rack from 2.2.4 to 2.2.6.4 in /docs

Bumps [rack](https://github.com/rack/rack) from 2.2.4 to 2.2.6.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@2.2.4...v2.2.6.4)

---
updated-dependencies:
- dependency-name: rack
  dependency-type: indirect
...

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

docs/Gemfile.lock

@@ -119,7 +119,7 @@ GEM
       coderay (~> 1.1)
       method_source (~> 1.0)
     racc (1.6.1)
-    rack (2.2.4)
+    rack (2.2.6.4)
     rack-proxy (0.6.5)
       rack
     rack-test (1.1.0)