Change anticipated group name to 'dev' in specs
Change anticipated group name to 'dev' in specs

This change is motivated by 2 things.
1. For Travis Enterprise, work-in-progress images are named with 'dev'.
  This is in documentation in customers' hands already.
2. Blue Box image creation process is not coupled with the name 'update'
  in any way.

So standardizing now to the name 'dev' makes sense.

travis-ci/travis-worker,ireznice/travis-worker,final-ci/travis-worker,gavioto/travis-worker,ireznice/travis-worker,final-ci/travis-worker,gavioto/travis-worker,travis-ci/travis-worker