[Security] Bump rack from 2.0.7 to 2.2.3

Bumps [rack](https://github.com/rack/rack) from 2.0.7 to 2.2.3. **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@2.0.7...2.2.3)

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

Gemfile.lock

@@ -153,7 +153,7 @@ GEM
     puma (3.12.0)
     pundit (2.0.0)
       activesupport (>= 3.0.0)
-    rack (2.0.7)
+    rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.3)