k8s-cloud-builder: Drop 'canary' variant
k8s-cloud-builder: Drop 'canary' variant

'canary' variant image builds are failing because kube-cross canary
images are not promoted to production (nor do I think they should be).

We can refactor some of this later and reintroduce the k8s-cloud-builder
canary image, but for now, let's not unintentionally mask other
failures by having the canary variant here.

Signed-off-by: Stephen Augustus <f96984fef9637085f0559f1484dfd4e99545cd6e@vmware.com>

kubernetes/release,kubernetes/release