Packet: Remove mayHaveUnreadBytes()

this was an old hack to prevent debug spam being emitted when we halted decoding of logins over breaking protocol changes. Since then, we've gone back to trying to decode the packet regardless, so this property is useless.

src/pocketmine/network/mcpe/protocol/LoginPacket.php

@@ -82,10 +82,6 @@ class LoginPacket extends DataPacket implements ServerboundPacket{
 		return true;
 	}
 
-	public function mayHaveUnreadBytes() : bool{
-		return $this->protocol !== null and $this->protocol !== ProtocolInfo::CURRENT_PROTOCOL;
-	}
-
 	protected function decodePayload() : void{
 		$this->protocol = $this->getInt();
 		$this->decodeConnectionRequest();