learning about how to make Akkoma's DB not be 6 GB

important command: `MIX_ENV=prod mix pleroma.database prune_objects --keep-threads --prune-orphaned-activities`

haven't ran it yet, will right after posting this, and will report back how useful it is
(screenshot attached for reference)

correcting myself, the commands appear for me to be `su akkoma -s $SHELL` (normal), then `MIX_ENV=prod ./bin/pleroma_ctl database prune_objects --keep-threads --prune-orphaned-activities`