kinder/ci/workflows: remove quotes around --ginkgo-flags
kinder/ci/workflows: remove quotes around --ginkgo-flags

Remove the quotes or this would fail parsing with:
  Error: flag "\"--skip=\\[MinimumKubeletVersion:(1.21)\\]\""
  could not be parsed correctly: the argument should start with '--'

kubernetes/kubeadm,kubernetes/kubeadm