ImagePage: Inherit parent's handling for action=render

ImagePage: Inherit parent's handling for action=render

ImagePage::render() was calling parent::view() instead of
parent::render(), thus skipping Article::render() entirely.
Therefore the logic to disable section edit links (and also,
to add an 'X-Robots-Tag: noindex' header) was not being used.
This fixes T65891 and T21415 for pages in 'File:' namespace.

Bug: T206546
Change-Id: I36ae716c9a363ae29b7a785cc41430301250baba