FallableTrait: add default implementation of tickFalling() to reduce Fallable pollution (#5350)

this is only used by concrete powder currently, so it doesn't make much sense to reimplement it in every implementor of Fallable.

src/block/Anvil.php

@@ -95,8 +95,4 @@ class Anvil extends Transparent implements Fallable{
 		}
 		return parent::place($tx, $item, $blockReplace, $blockClicked, $face, $clickVector, $player);
 	}
-
-	public function tickFalling() : ?Block{
-		return null;
-	}
 }