The documentation doesn't mention that `matrix_rtc` only works when msc4143_enabled is enabled.

[Half-Shot]

Description

https://element-hq.github.io/synapse/latest/usage/configuration/config_documentation.html?highlight=rtc#matrix_rtc should call this out.

Steps to reproduce

N/A docs

Homeserver

N/A docs

Synapse Version

1.144.0

Installation Method

Other (please mention below)

Database

N/A

Workers

Single process

Platform

N/A

Configuration

N/A

Relevant log output

N/A

Anything else that would be useful to know?

N/A