Update go mod and vendor in client dir to 0.28.0

client/vendor/k8s.io/api/rbac/v1/generated.proto

@@ -66,6 +66,7 @@ message ClusterRoleBinding {
 
   // RoleRef can only reference a ClusterRole in the global namespace.
   // If the RoleRef cannot be resolved, the Authorizer must return an error.
+  // This field is immutable.
   optional RoleRef roleRef = 3;
 }
 
@@ -140,6 +141,7 @@ message RoleBinding {
 
   // RoleRef can reference a Role in the current namespace or a ClusterRole in the global namespace.
   // If the RoleRef cannot be resolved, the Authorizer must return an error.
+  // This field is immutable.
   optional RoleRef roleRef = 3;
 }