Homogenize rails help output

In commit 6567464b we homogenized rails
commands with former rake tasks. We decided to display all commands at
the same level and merged the list of commands displayed by `rails help`.

We however forgot to actually merge the output in the command itself.
This commit fixes that.

railties/lib/rails/command.rb

@@ -83,20 +83,21 @@ def root
       end
 
       def print_commands # :nodoc:
-        sorted_groups.each { |b, n| print_list(b, n) }
+        commands.each { |command| puts("  #{command}") }
       end
 
-      def sorted_groups # :nodoc:
-        lookup!
+      private
+        COMMANDS_IN_USAGE = %w(generate console server test test:system dbconsole new)
+        private_constant :COMMANDS_IN_USAGE
 
-        groups = (subclasses - hidden_commands).group_by { |c| c.namespace.split(":").first }
-        groups.transform_values! { |commands| commands.flat_map(&:printing_commands).sort }
+        def commands
+          lookup!
 
-        rails = groups.delete("rails")
-        [[ "rails", rails ]] + groups.sort.to_a
-      end
+          visible_commands = (subclasses - hidden_commands).flat_map(&:printing_commands)
+
+          (visible_commands - COMMANDS_IN_USAGE).sort
+        end
 
-      private
         def command_type # :doc:
           @command_type ||= "command"
         end