Bump rack from 2.0.7 to 2.0.8 in /6.secrets/cool-app

Bumps [rack](https://github.com/rack/rack) from 2.0.7 to 2.0.8.
- [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/2.0.7...2.0.8)
Signed-off-by: dependabot[bot] <support@github.com>

6.secrets/cool-app/Gemfile.lock

@@ -117,7 +117,7 @@ GEM
     popper_js (1.14.5)
     public_suffix (3.1.0)
     puma (3.12.1)
-    rack (2.0.7)
+    rack (2.0.8)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.3)