Bump sinatra from 2.0.3 to 2.0.4 (#777) [ci skip]

Bumps [sinatra](https://github.com/sinatra/sinatra) from 2.0.3 to 2.0.4.
- [Release notes](https://github.com/sinatra/sinatra/releases)
- [Changelog](https://github.com/sinatra/sinatra/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sinatra/sinatra/compare/v2.0.3...v2.0.4)

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

Gemfile.lock

@@ -582,7 +582,7 @@ GEM
     multi_json (1.13.1)
     multi_xml (0.6.0)
     multipart-post (2.0.0)
-    mustermann (1.0.2)
+    mustermann (1.0.3)
     nakayoshi_fork (0.0.4)
     naught (1.1.0)
     nenv (0.3.0)
@@ -651,7 +651,7 @@ GEM
     rack (2.0.5)
     rack-host-redirect (1.3.0)
       rack
-    rack-protection (2.0.3)
+    rack-protection (2.0.4)
       rack
     rack-proxy (0.6.4)
       rack
@@ -805,10 +805,10 @@ GEM
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sinatra (2.0.3)
+    sinatra (2.0.4)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.3)
+      rack-protection (= 2.0.4)
       tilt (~> 2.0)
     skylight (2.0.2)
       skylight-core (= 2.0.2)