The file in question is now here: https://github.com/twitter/the-algorithm/blob/main/home-mixe...

author_is_elon, author_is_democrat, and author_is_republican are in fact gone. Now there is grok_politics_neutral, grok_politics_left, and grok_politics_right. This is in addition to a whole group of other categories, such as grok_category_sports and grok_category_music. All are based on annotations by Grok.

Importantly, this file is not used for recommendations. Everything in this file is only used for "metrics tracking purposes to measure how often we serve posts with various attributes." This would also have applied to author_is_elon.