Merge pull request #203 from alphagov/dependabot/bundler/rack-2.2.20

Author: govuk-ci

Gemfile.lock

@@ -167,7 +167,7 @@ GEM
     prism (1.4.0)
     public_suffix (6.0.2)
     racc (1.8.1)
-    rack (2.2.19)
+    rack (2.2.20)
     rack-livereload (0.3.17)
       rack
     rainbow (3.1.1)