Bump rack from 2.0.8 to 2.1.4 in /environments/ruby (#1654)

Bumps [rack](https://github.com/rack/rack) from 2.0.8 to 2.1.4.
- [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/2.0.8...2.1.4)

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environments/ruby/Gemfile.lock

@@ -3,7 +3,7 @@ GEM
   specs:
     daemons (1.3.1)
     eventmachine (1.2.7)
-    rack (2.0.8)
+    rack (2.1.4)
     thin (1.7.2)
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)