Bump rack from 2.0.6 to 2.0.8

Bumps [rack](https://github.com/rack/rack) from 2.0.6 to 2.0.8.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](rack/rack@2.0.6...2.0.8)

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

Author: dependabot[bot]

Gemfile.lock

@@ -113,7 +113,7 @@ GEM
     parser (2.3.3.1)
       ast (~> 2.2)
     public_suffix (3.0.3)
-    rack (2.0.6)
+    rack (2.0.8)
     rack-livereload (0.3.17)
       rack
     rake (12.3.1)