Update owners.

        DEPRECATED:  use ``policy["roles/owners"] = value`` instead.

def owners(self, value):
        """Update owners.

        DEPRECATED:  use ``policy["roles/owners"] = value`` instead."""
        warnings.warn(
            _ASSIGNMENT_DEPRECATED_MSG.format("owners", OWNER_ROLE), DeprecationWarning
        )
        self[OWNER_ROLE] = value