Bump rack from 2.2.8 to 2.2.8.1 in /webapp/ruby

Bumps [rack](https://github.com/rack/rack) from 2.2.8 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@v2.2.8...v2.2.8.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

webapp/ruby/Gemfile.lock

@@ -8,7 +8,7 @@ GEM
     mysql2 (0.5.5)
     mysql2-cs-bind (0.0.6)
       mysql2
-    rack (2.2.8)
+    rack (2.2.8.1)
     rack-protection (2.2.3)
       rack
     raindrops (0.16.0)