Move System::jsonExit to BaseModule->jsonExit

- This will ensure headers set in BaseModule->run will be carried in jsonExit scenarios
- Deprecate jsonExit() method in Core\System

src/Module/Api/Mastodon/Timelines/Home.php

@@ -101,6 +101,6 @@ class Home extends BaseApi
 
 
 		self::setLinkHeader($request['friendica_order'] != TimelineOrderByTypes::ID);
-		System::jsonExit($statuses);
+		$this->jsonExit($statuses);
 	}
 }