revert required field

Author: giancarloromeo

packages/models-library/src/models_library/api_schemas_directorv2/clusters.py

@@ -125,7 +125,6 @@ class ClusterCreate(BaseCluster):
                     "name": "My awesome cluster",
                     "type": ClusterTypeInModel.ON_PREMISE,
                     "endpoint": "https://registry.osparc-development.fake.dev",
-                    "owner": None,
                     "authentication": {
                         "type": "simple",
                         "username": "someuser",