Bump sinatra from 2.0.5 to 2.0.6

Bumps [sinatra](https://github.com/sinatra/sinatra) from 2.0.5 to 2.0.6.
- [Release notes](https://github.com/sinatra/sinatra/releases)
- [Changelog](https://github.com/sinatra/sinatra/blob/master/CHANGELOG.md)
- [Commits](sinatra/sinatra@v2.0.5...v2.0.6)

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

Author: dependabot-preview[bot]

Gemfile.lock

@@ -3,14 +3,14 @@ GEM
   specs:
     mustermann (1.0.3)
     rack (2.0.7)
-    rack-protection (2.0.5)
+    rack-protection (2.0.6)
       rack
     redis (4.1.0)
     simple-random (1.0.3)
-    sinatra (2.0.5)
+    sinatra (2.0.6)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.5)
+      rack-protection (= 2.0.6)
       tilt (~> 2.0)
     split (3.3.2)
       redis (>= 2.1)