Set default loglevel to `warn` in prod

It's rare that info logs are needed to debug the issue, so I would
suggest setting them to warn in prod by default to make finding the
relevant parts easier and potentially even decrease cpu usage on bigger
instances

Closes #962

CHANGELOG.md

@@ -64,6 +64,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Federation: Expand the audience of delete activities to all recipients of the deleted object
 - Federation: Removed `inReplyToStatusId` from objects
 - Configuration: Dedupe enabled by default
+- Configuration: Default log level in `prod` environment is now set to `warn`
 - Configuration: Added `extra_cookie_attrs` for setting non-standard cookie attributes. Defaults to ["SameSite=Lax"] so that remote follows work.
 - Timelines: Messages involving people you have blocked will be excluded from the timeline in all cases instead of just repeats.
 - Admin API: Move the user related API to `api/pleroma/admin/users`

config/prod.exs

@@ -18,7 +18,7 @@
   protocol: "http"
 
 # Do not print debug messages in production
-config :logger, level: :info
+config :logger, level: :warn
 
 # ## SSL Support
 #