Bump sinatra from 2.0.8.1 to 2.2.0

Bumps [sinatra](https://github.com/sinatra/sinatra) from 2.0.8.1 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@v2.0.8.1...v2.2.0)

---
updated-dependencies:
- dependency-name: sinatra
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Gemfile.lock

@@ -1,25 +1,23 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    backports (3.17.2)
-    multi_json (1.14.1)
+    multi_json (1.15.0)
     mustermann (1.1.1)
       ruby2_keywords (~> 0.0.1)
     rack (2.2.3)
-    rack-protection (2.0.8.1)
+    rack-protection (2.2.0)
       rack
-    ruby2_keywords (0.0.2)
-    sinatra (2.0.8.1)
+    ruby2_keywords (0.0.5)
+    sinatra (2.2.0)
       mustermann (~> 1.0)
-      rack (~> 2.0)
-      rack-protection (= 2.0.8.1)
+      rack (~> 2.2)
+      rack-protection (= 2.2.0)
       tilt (~> 2.0)
-    sinatra-contrib (2.0.8.1)
-      backports (>= 2.8.2)
+    sinatra-contrib (2.2.0)
       multi_json
       mustermann (~> 1.0)
-      rack-protection (= 2.0.8.1)
-      sinatra (= 2.0.8.1)
+      rack-protection (= 2.2.0)
+      sinatra (= 2.2.0)
       tilt (~> 2.0)
     sinatra-jsonp (0.5.0)
       multi_json (~> 1.8)