[ticket/12557] Fix doc block errors found by Sami for ascraeus

Companion of #2472 with more corrections for 3.1.

[PHPBB3-12557](https://tracker.phpbb.com/browse/PHPBB3-12557)
there isn't any parent class, so you can't use @inheritdoc
also, @inheritdoc isn't valid, you should use {@inheritdoc} instead