Out of date installation instructions and resources

### Current Behavior

From a slack chat in dept-eng

* Mosquitto is still mentioned in the Broker Configuration section: https://flowfuse.com/docs/install/configuration/#mqtt-broker-configuration-1
* docker quickstart compose file still contains mosquitto (and is using un tagged image names)

### Expected Behavior

should be valid and up to date

### Steps To Reproduce

na

### Environment

- FlowFuse version:
- Node.js version:
- npm version:
- Platform/OS:
- Browser:

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate