Bump rack from 2.2.7 to 2.2.8

Bumps [rack](https://github.com/rack/rack) from 2.2.7 to 2.2.8.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/main/CHANGELOG.md)
- [Commits](https://github.com/rack/rack/compare/v2.2.7...v2.2.8)

---
updated-dependencies:
- dependency-name: rack
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Gemfile

@@ -33,7 +33,7 @@ gem 'kramdown'
 gem 'liquid'
 gem 'listen'
 gem 'mercenary'
-gem 'rack', '~> 2.2.7'
+gem 'rack', '~> 2.2.8'
 gem 'railties', '>= 5.2.2.1'
 gem 'rouge'
 gem 'rubocop'

Gemfile.lock

@@ -192,7 +192,7 @@ GEM
       ttfunk
     public_suffix (5.0.3)
     racc (1.7.1)
-    rack (2.2.7)
+    rack (2.2.8)
     rack-test (2.1.0)
       rack (>= 1.3)
     rails-dom-testing (2.1.1)
@@ -292,7 +292,7 @@ DEPENDENCIES
   mini_racer (~> 0.8.0)
   minima
   nokogiri (>= 1.10.4)
-  rack (~> 2.2.7)
+  rack (~> 2.2.8)
   railties (>= 5.2.2.1)
   rouge
   rubocop