`turso db update` is misleading because it updates the group

[penberg]

If you run turso db update, you will update the database software on all the databases in the same group. We should consider renaming the command to turso groups system-upgrade or something.

[avinassh]

How about this:

1. If its a non group DB, we will update it
2. If its a group DB, we fail saying that to update they need to turso groups update

We can decide whether we want to call system-upgrade or something else.