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: Id328f169004a6cb69078b58801885b00581fee33
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@digia.com>