chore(deps): bump rack from 2.2.6.3 to 2.2.6.4 in /tests/apps/ruby

Bumps [rack](https://github.com/rack/rack) from 2.2.6.3 to 2.2.6.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](https://github.com/rack/rack/compare/v2.2.6.3...v2.2.6.4)

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

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

tests/apps/ruby/Gemfile.lock

@@ -5,7 +5,7 @@ GEM
     eventmachine (1.2.7)
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
-    rack (2.2.6.3)
+    rack (2.2.6.4)
     rack-protection (3.0.5)
       rack
     ruby2_keywords (0.0.5)