Bump rack from 2.0.9 to 2.1.4 (#116)

Bumps [rack](https://github.com/rack/rack) from 2.0.9 to 2.1.4.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rack/rack/compare/2.0.9...2.1.4)

Signed-off-by: dependabot[bot] <[e-mail]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Gemfile

···
 
 ruby ">= 2.4.0"
 
-gem "rack", "~> 2.0.0"
+gem "rack", "~> 2.1.4"
 
 gem "sinatra", "~> 2.0.0"
 gem "sinatra-contrib", "~> 2.0.0"

Gemfile.lock

···
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (4.0.3)
-    rack (2.0.9)
+    rack (2.1.4)
     rack-protection (2.0.8.1)
       rack
     rack-test (1.1.0)
···
   minitest
   pbkdf2-ruby
   pry
-  rack (~> 2.0.0)
+  rack (~> 2.1.4)
   rack-test
   rake
   rotp