sync.profile: Point dependencies to 'refs/heads/dev'

We should test dev branches against dev branches only by default.
At some point we should automate the merges from release->stable->dev
and/or decide how to handle possible conflicts.

This is good enough for the time being.

Change-Id: I40b8d45fa5f6106912ad0a5f9ae69fae7b9ec660
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>