Bump rack from 3.1.14 to 3.1.21

Bumps [rack](https://github.com/rack/rack) from 3.1.14 to 3.1.21.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](rack/rack@v3.1.14...v3.1.21)

---
updated-dependencies:
- dependency-name: rack
  dependency-version: 3.1.21
  dependency-type: indirect
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -126,7 +126,7 @@ GEM
       forwardable-extended (~> 2.6)
     public_suffix (7.0.5)
     racc (1.8.0)
-    rack (3.1.14)
+    rack (3.1.21)
     rake (13.2.1)
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)