Fix dereferenced_target naming in Gitlab::Git::Ref initialize

lib/gitlab/git/ref.rb

@@ -33,9 +33,9 @@ module Gitlab
         object
       end
 
-      def initialize(repository, name, target, derefenced_target)
+      def initialize(repository, name, target, dereferenced_target)
         @name = Gitlab::Git.ref_name(name)
-        @dereferenced_target = derefenced_target
+        @dereferenced_target = dereferenced_target
         @target = if target.respond_to?(:oid)
                     target.oid
                   elsif target.respond_to?(:name)