Clean up video parameters from `settings.yml` files

[jotaen4tinypilot]

Follow up of https://github.com/tiny-pilot/tinypilot/issues/1267 (which this is blocked on).

After we have removed writing the defaults to settings.yml, we should clean up the corresponding values that we had already written on existing installations.

That’s mostly a precautionary measure, to avoid surprises in the future.