Bump rack from 2.2.6.4 to 2.2.8.1 in /api/ruby/basics-of-authentication

Bumps [rack](https://github.com/rack/rack) from 2.2.6.4 to 2.2.8.1.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.6.4...v2.2.8.1)

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

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

Author: dependabot[bot]

api/ruby/basics-of-authentication/Gemfile.lock

@@ -9,7 +9,7 @@ GEM
     mustermann (2.0.2)
       ruby2_keywords (~> 0.0.1)
     netrc (0.11.0)
-    rack (2.2.6.4)
+    rack (2.2.8.1)
     rack-protection (2.2.3)
       rack
     rest-client (1.8.0)