Clarify Privacy Consideration around stub stack

[mcmanus]

A browser that has both a stub resolver stack and a TLS stack that is independent of HTTP
could make a DoT connection to the resolver being used by the operating system.

This is true - it could be more clear that this is a trial connection to the resolver to see if it does dot.

more importantly, I'm not sure what the reader is being asked to do with this statement in the context of the draft. Maybe it should be consolidated with the text of the last security consideration instead ("there is currently no way.."