Merge pull request #1241 from k8s-infra-cherrypick-robot/cherry-pick-1240-to-release-0.6

[release-0.6]  🐛 remove webhooks for old APIversion v1alpha4

Author: k8s-ci-robot

api/v1alpha4/identity_types.go

@@ -16,8 +16,6 @@ limitations under the License.
 
 package v1alpha4
 
-const defaultIdentityRefKind = "Secret"
-
 // OpenStackIdentityReference is a reference to an infrastructure
 // provider identity to be used to provision cluster resources.
 type OpenStackIdentityReference struct {