Don't subscribe to mqtt topic if downlink is not on

[RCGV1]

What changed?

Don't subscribe to mqtt topic if downlink is not on

Why did it change?

Subscribing to the mqtt topic is not needed since we do not need to downlink data if we are just going to discard it. We are sending a lot of extra data to the node for no reason for it to be thrown out.

How is this tested?

Tested that downlink and uplink still works and tried changing the channel settings.
I made sure that uplink still works if we are not subscribed to the topic.

Screenshots/Videos (when applicable)

Checklist

• My code adheres to the project's coding and style guidelines.
• I have conducted a self-review of my code.
• I have commented my code, particularly in complex areas.
• I have verified whether these changes require an update to existing documentation or if new documentation is needed, and created an issue in the docs repo if applicable.
• I have tested the change to ensure that it works as intended.