docs: fix getting-started.md for vmis
docs: fix getting-started.md for vmis

Fix getting-started.md since vmi-ephemeral
as used in the examples is now a vmi instance
and not a vm one.

stu-gott/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,davidvossel/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,stu-gott/kubevirt,kubevirt/kubevirt,stu-gott/kubevirt,davidvossel/kubevirt,kubevirt/kubevirt