Bump rack from 1.6.11 to 1.6.13

Bumps [rack](https://github.com/rack/rack) from 1.6.11 to 1.6.13.
- [Release notes](https://github.com/rack/rack/releases)
- [Changelog](https://github.com/rack/rack/blob/master/CHANGELOG.md)
- [Commits](rack/rack@1.6.11...1.6.13)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile.lock

@@ -114,7 +114,7 @@ GEM
       byebug (~> 11.0)
       pry (~> 0.10)
     public_suffix (4.0.1)
-    rack (1.6.11)
+    rack (1.6.13)
     rack-accept (0.4.5)
       rack (>= 0.4)
     rack-test (1.1.0)