chore(deps): bump rack from 2.2.17 to 2.2.18 in /tests/apps/ruby

Bumps [rack](https://github.com/rack/rack) from 2.2.17 to 2.2.18.
- [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/v2.2.17...v2.2.18)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.18
  dependency-type: indirect
...

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

tests/apps/ruby/Gemfile.lock

@@ -7,7 +7,7 @@ GEM
     logger (1.7.0)
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
-    rack (2.2.17)
+    rack (2.2.18)
     rack-protection (3.2.0)
       base64 (>= 0.1.0)
       rack (~> 2.2, >= 2.2.4)