build(deps): bump rackup from 2.1.0 to 2.2.1 in /assets/ruby_simple

Bumps [rackup](https://github.com/rack/rackup) from 2.1.0 to 2.2.1.
- [Release notes](https://github.com/rack/rackup/releases)
- [Changelog](https://github.com/rack/rackup/blob/main/releases.md)
- [Commits](rack/rackup@v2.1.0...v2.2.1)

---
updated-dependencies:
- dependency-name: rackup
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

assets/ruby_simple/Gemfile.lock

@@ -4,15 +4,14 @@ GEM
     base64 (0.2.0)
     mustermann (3.0.0)
       ruby2_keywords (~> 0.0.1)
-    rack (3.0.9.1)
+    rack (3.1.8)
     rack-protection (4.0.0)
       base64 (>= 0.1.0)
       rack (>= 3.0.0, < 4)
     rack-session (2.0.0)
       rack (>= 3.0.0)
-    rackup (2.1.0)
+    rackup (2.2.1)
       rack (>= 3)
-      webrick (~> 1.8)
     ruby2_keywords (0.0.5)
     sinatra (4.0.0)
       mustermann (~> 3.0)