Merge pull request #1099 from scala/dependabot/bundler/rack-1.6.12

Bump rack from 1.6.11 to 1.6.12

Author: SethTisue

Gemfile.lock

@@ -65,7 +65,7 @@ GEM
     pathutil (0.16.2)
       forwardable-extended (~> 2.6)
     public_suffix (3.0.3)
-    rack (1.6.11)
+    rack (1.6.12)
     rack-jekyll (0.5.0)
       jekyll (>= 1.3)
       listen (>= 1.3)