unused method `db.sublevel` removed

[mixmix]

I've removed this in ssb-db@20.0.1

I'm leaving this issue here so that if a problem turns up people will find this and we can revert

[stale]

Is this still relevant? If so, what is blocking it? Is there anything you can do to help move it forward?

[mixmix]

Please keep this open

[stale]

Is this still relevant? If so, what is blocking it? Is there anything you can do to help move it forward?