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: Ib08372b619eda3a1faf382f2fe44c3acc88f9e1f
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@digia.com>