Documentation for the opensource version of lwm2m plugin contains references to the enterprise features

File: [/en_US/modules/lwm2m_protocol.md](https://docs.emqx.io/en/broker/v4.3/modules/lwm2m_protocol.html)
This document contains instruction to configure lwm2m module. However the opensource version of the broker uses a plugin rather than module. The instruction should be updated to use a different way to configure the plugin.

Open en_US/modules/lwm2m_protocol.md and review the configuration instructions for the open source broker. Compare the documented module setup with the plugin-based setup described by the issue. Done means the document no longer refers to enterprise module features and explains how to configure the plugin instead.

Written by the indexing model from the issue text.