build(deps): [security] bump rack from 2.0.6 to 2.2.2

Bumps [rack](https://github.com/rack/rack) from 2.0.6 to 2.2.2. **This update includes security fixes.**
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](rack/rack@2.0.6...v2.2.2)

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

Gemfile.lock

@@ -140,7 +140,7 @@ GEM
     pg (1.1.3)
     public_suffix (3.0.3)
     puma (3.12.0)
-    rack (2.0.6)
+    rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.2)