Bump sinatra from 2.1.0 to 2.2.0

Bumps [sinatra](https://github.com/sinatra/sinatra) from 2.1.0 to 2.2.0.
- [Release notes](https://github.com/sinatra/sinatra/releases)
- [Changelog](https://github.com/sinatra/sinatra/blob/master/CHANGELOG.md)
- [Commits](sinatra/sinatra@v2.1.0...v2.2.0)

---
updated-dependencies:
- dependency-name: sinatra
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -4,15 +4,15 @@ GEM
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
     rack (2.2.3)
-    rack-protection (2.1.0)
+    rack-protection (2.2.0)
       rack
     redis (4.5.1)
     ruby2_keywords (0.0.5)
     rubystats (0.3.0)
-    sinatra (2.1.0)
+    sinatra (2.2.0)
       mustermann (~> 1.0)
       rack (~> 2.2)
-      rack-protection (= 2.1.0)
+      rack-protection (= 2.2.0)
       tilt (~> 2.0)
     split (4.0.1)
       redis (>= 4.2)