Apply changes to auto_link_user? method

lib/gitlab/auth/o_auth/user.rb

@@ -274,11 +274,10 @@ module Gitlab
 
         def auto_link_user?
           auto_link = Gitlab.config.omniauth.auto_link_user
-          if auto_link.is_a?(Array)
-            auto_link.include?(auth_hash.provider)
-          else
-            auto_link
-          end
+          return auto_link if [true, false].include?(auto_link)
+
+          auto_link = Array(auto_link)
+          auto_link.include?(auth_hash.provider)
         end
       end
     end