Bump rack from 2.0.8 to 2.2.3

Bumps [rack](https://github.com/rack/rack) from 2.0.8 to 2.2.3.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](rack/rack@2.0.8...2.2.3)

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

Author: dependabot[bot]

Gemfile.lock

@@ -12,7 +12,7 @@ GEM
     mustermann (1.0.3)
     net-http-persistent (3.0.0)
       connection_pool (~> 2.2)
-    rack (2.0.8)
+    rack (2.2.3)
     rack-protection (2.0.5)
       rack
     sinatra (2.0.5)