Player: Explicitly clear permission recalculation callbacks

this is necessary to get rid of the broadcast permission callbacks, which retain references to the Player itself, forming a cycle which would prevent PermissibleBase->__destruct() from cleaning up.

src/player/Player.php

@@ -2006,6 +2006,8 @@ class Player extends Human implements CommandSender, ChunkListener, IPlayer{
 		$this->removeCurrentWindow();
 		$this->removePermanentInventories();
 
+		$this->perm->getPermissionRecalculationCallbacks()->clear();
+
 		$this->flagForDespawn();
 	}