Revert "Update channel 1.15 k8s recommendation to 1.15.12"
Revert "Update channel 1.15 k8s recommendation to 1.15.12"

This reverts commit 99975e867ff4eeb4eed8e95f52cd4a425f2542da.

kubernetes/kops,kubernetes/kops,kubernetes/kops,justinsb/kops,justinsb/kops,justinsb/kops