Some more restructuring

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Db/Card.php

@@ -159,5 +159,4 @@ class Card extends RelationalEntity {
 	public function getCalendarPrefix(): string {
 		return 'card';
 	}
-
 }

lib/Db/Stack.php

@@ -65,5 +65,4 @@ class Stack extends RelationalEntity {
 	public function getCalendarPrefix(): string {
 		return 'stack';
 	}
-
 }