Only enqueue story for CoreNLP annotation / mark story as processed when there are no remaining story downloads to be fetched
Remove unnecessary package prefix
Enqueue CoreNLP Gearman jobs by stories_id (not by downloads_id)
Use a shorthand variable $stories_id
Re-enqueue a CoreNLP annotation job after each call to update_story_sentence_words_and_language() just to make sure that all sentences get re-annotated on each sentence change