Akmalfairuz

### Impact Due to a workaround for an old client bug (which has since been fixed), very large JSON payloads in `ModalFormResponsePacket` were able to cause the server to spend a significant amount of time processing the packet. Large numbers of these packets were able to hog CPU time so as to prevent the server from processing other connections in a timely manner. ### Patches The problem has been addressed in 3baa5ab71214f96e6e7ab12cb9beef08118473b5 by removing the workaround code. ### Workarounds Plugins could cancel `DataPacketReceiveEvent` for this packet, decode the data their way, and then call `Player->onFormSubmit()` directly, bypassing the vulnerable code.