Update queue documentation to preferred Civi::queue

The documentation currently refers to an earlier way to instantiate the queue - I couldn't see any reason to use anything other than \Civi::queue since the 2 functions seemed to be basically 'is reset being passed in or not' and we really want to give one recommended method rather than lots of 'choice for choice's sake'

However - it might make sense to move the other methods to a separate 'legacy queue interaction' session

@totten I'm currently looking at your queue work & the docs & trying to get to the point of it all making sense....