[Security] Bump rack from 2.0.7 to 2.1.1

Bumps [rack](https://github.com/rack/rack) from 2.0.7 to 2.1.1. **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...2.1.1)

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

Gemfile.lock

@@ -128,7 +128,7 @@ GEM
     pry-rescue (1.5.0)
       interception (>= 0.5)
       pry (>= 0.12.0)
-    rack (2.0.7)
+    rack (2.1.1)
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (5.0.7.2)