v0.0.2b6

Pre-release.

Fix

• Do not carry the v1 registry onto the derived v2 image.

ImageSpec.registry records where the v1 image was pulled from, which is not necessarily
somewhere the cluster may push to. Carrying it over made the derived build target
public.ecr.aws/unionai/flytekit, which the image builder has no push credentials for, so the
build succeeded and then failed on export:

#15 ERROR: failed to push public.ecr.aws/unionai/flytekit:c26bfcf523... 401 Unauthorized

The registry is now left unset, so the remote builder pushes to the backend's own default
registry and the target becomes a bare flytekit:<hash>. The image name is still propagated,
since Image.clone refuses to add layers to an unnamed image.