Update rack gem to version 2.2.3.1

Merge branch 'security-rack-2-2-3-1-14-10' into '14-10-stable-ee'

See merge request gitlab-org/security/gitlab!2554

Changelog: security

Gemfile.lock

@@ -958,7 +958,7 @@ GEM
     pyu-ruby-sasl (0.0.3.3)
     raabro (1.1.6)
     racc (1.6.0)
-    rack (2.2.3)
+    rack (2.2.3.1)
     rack-accept (0.4.5)
       rack (>= 0.4)
     rack-attack (6.3.0)

qa/Gemfile.lock

@@ -251,7 +251,7 @@ GEM
       pry (~> 0.10)
     public_suffix (4.0.6)
     racc (1.6.0)
-    rack (2.2.3)
+    rack (2.2.3.1)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rainbow (3.0.0)

tooling/overcommit/Gemfile.lock

@@ -34,7 +34,7 @@ GEM
     parallel (1.19.2)
     parser (2.7.2.0)
       ast (~> 2.4.1)
-    rack (2.2.3)
+    rack (2.2.3.1)
     rainbow (3.0.0)
     regexp_parser (1.8.2)
     rexml (3.2.4)