Fix supervisor repository regex
Fix supervisor repository regex

Update the supervisor repository regex so the supervisor version can be
correctly extracted from the images.

Change-type: patch
Signed-off-by: Alex Gonzalez <59ce0f63e40328cff03fa578b2b98f47829af4e6@balena.io>
resin-io/resin-preload-image-script,resin-io/resin-preload-image-script