Port 8448 is not enabled from inside the Docker container

### Background information
- **Dendrite version**: Dendrite 0.14.1+40bef6a
- **SQLite3 or Postgres?**: Postgres
- **Running in Docker?**: Docker
- **`go version`**: go1.22.2

### Description
- **What** is the problem: Port 8448 is not enabled by default from inside the Docker container. [The example docker-compose.yml](https://github.com/element-hq/dendrite/blob/main/build/docker/docker-compose.yml) contains
```
ports:
- 8008:8008
- 8448:8448
```
Despite that, the port 8448 does not listen for anything. To test it, I launched a shell from inside the docker container: `docker exec -it /bin/sh` and this is the output of `netstat -tuln:`

```
Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 127.0.0.11:45021 0.0.0.0:* LISTEN
tcp 0 0 :::8008 :::* LISTEN
udp 0 0 127.0.0.11:41453 0.0.0.0:*
```

As you can see, 8008 is correctly listed; 8448 is not.

- **Who** is affected: Every system mantainer using the latest Docker image I guess
- **How** is this bug manifesting: No response on 8448

### Steps to reproduce

- Download the .yml file from [here](https://github.com/element-hq/dendrite/blob/main/build/docker/docker-compose.yml)
- `docker-compose up -d`