Template settings include Dashboard URL path that only applies to node-red-dashboard

[knolleary]

We added the Dashboard URL path option to the instance settings template before DB2 was a thing.

With node-red-dashboard deprecated and focus on DB2, this setting is misleading as it has no affect on DB2 path.

We need to decide how to handle this.

Options:

1. Remove the option
2. Clarify text that this only applies to node-red-dashboard - that is what it currently says, but relies on user knowing the subtle different
3. Update DB2 to allow the root path to be customised and then apply this setting - could cause issues if user has both old and new dashboards installed as they will both try to use the same path
4. Something else...