[Security] Bump rack from 2.0.5 to 2.0.6 (#9214)

Bumps [rack](https://github.com/rack/rack) from 2.0.5 to 2.0.6. **This update includes security fixes.**
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rack/rack/compare/2.0.5...2.0.6)

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

Gemfile.lock

@@ -420,7 +420,7 @@ GEM
     pundit (2.0.0)
       activesupport (>= 3.0.0)
     raabro (1.1.6)
-    rack (2.0.5)
+    rack (2.0.6)
     rack-attack (5.4.2)
       rack (>= 1.0, < 3)
     rack-cors (1.0.2)