unneeded delete transitions and marking methods in the Workflow Handler

The deleteWorkflowMetadata() method implemented in WorkflowHandler.php is using two unnecessary methods:

• deleteTransitionMetadataForWorkflow()
• deleteMarkingForWorkflow()

I noticed in the ezeditorialworkflow_transitions and ezeditorialworkflow_markings table definition following constraints:

CONSTRAINT `fk_ezeditorialworkflow_markings_workflow_id` FOREIGN KEY (`workflow_id`) REFERENCES `ezeditorialworkflow_workflows` (`id`) ON DELETE CASCADE

and

CONSTRAINT `fk_ezeditorialworkflow_transitions_workflow_id` FOREIGN KEY (`workflow_id`) REFERENCES `ezeditorialworkflow_workflows` (`id`) ON DELETE CASCADE

which has a referential action for a foreign key that allows us to delete data from child/related tables automatically when we delete the data from the parent table ezeditorialworkflow_workflows.

We can remove some methods in the Handler and the Gateway as well and just keep the deleteWorkflowMetadata() method