Adjust fake manager

Signed-off-by: Joas Schilling <coding@schilljs.com>

tests/lib/Comments/FakeManager.php

@@ -142,7 +142,7 @@ class FakeManager implements ICommentsManager {
 		return [];
 	}
 
-	public function deleteMessageExpiredAtObject(string $objectType, string $objectId): bool {
+	public function deleteCommentsExpiredAtObject(string $objectType, string $objectId = ''): bool {
 		return true;
 	}
 }