Bump rack from 2.2.18 to 2.2.20

Bumps [rack](https://github.com/rack/rack) from 2.2.18 to 2.2.20.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v2.2.18...v2.2.20)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 2.2.20
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -168,7 +168,7 @@ GEM
     parslet (2.0.0)
     public_suffix (5.0.1)
     racc (1.8.1)
-    rack (2.2.18)
+    rack (2.2.20)
     rack-livereload (0.3.17)
       rack
     rainbow (3.1.1)