Add changelog entry

CHANGELOG.md

@@ -10,12 +10,18 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Config: HTTP timeout options, :pool\_timeout and :receive\_timeout
 - Added statistic gathering about instances which do/don't have signed fetches when they request from us
 - Ability to set a default post expiry time, after which the post will be deleted. If used in concert with ActivityExpiration MRF, the expiry which comes _sooner_ will be applied.
+- Regular task to prune local transient activities
+- Task to manually run the transient prune job (pleroma.database prune\_task)
 
 ## Changed
 - MastoAPI: Accept BooleanLike input on `/api/v1/accounts/:id/follow` (fixes follows with mastodon.py)
 - Relays from akkoma are now off by default
 - NormalizeMarkup MRF is now on by default
 - Follow/Block/Mute imports now spin off into *n* tasks to avoid the oban timeout
+- Transient activities recieved from remote servers are no longer persisted in the database
+
+## Upgrade Notes
+- If you have an old instance, you will probably want to run `mix pleroma.database prune_task` in the foreground to catch it up with the history of your instance.
 
 ## 2022.11