Disable federation by default (#20045) (#20046)

* Disable federation by default (#20045)

- Backport #20045
  - A Gitea instance should choose whetever they want to federate(as once it has more features also brings extra costs/moderation/unexpected behavior) with other AP/ForgeFed software.

* Fix tests

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -1088,7 +1088,7 @@ Task queue configuration has been moved to `queue.task`. However, the below conf
 
 ## Federation (`federation`)
 
-- `ENABLED`: **true**: Enable/Disable federation capabilities
+- `ENABLED`: **false**: Enable/Disable federation capabilities
 - `SHARE_USER_STATISTICS`: **true**: Enable/Disable user statistics for nodeinfo if federation is enabled
 
 ## Packages (`packages`)