- remove code to manually archive/unarchive articles
- remove ttrss_archived_feeds/orig_feed_id handling - the whole thing was implemented for
this data to be kept indefinitely; it doesn't make a lot of sense to deal with this stuff
now that it is expired after one month anyway (same reasons as feed browser being removed - privacy)
- remove "originally from"-related stuff because of the above
- also remove unused remaining frontend/backend code related to feed browser (rip)