Stop forwarding SagaAudit messages from the primary instance to the audit instance

The primary instance forwards SagaAudit message to the audit instance and logs a warning:

ServiceControl/src/ServiceControl/SagaAudit/SagaUpdatedHandler.cs

Lines 28 to 30 in 6fe6ede

    
           // TODO Forward saga audit messages and warn in ServiceControl 5, remove in 6 
        
           log.WarnFormat("Configure the Saga Audit plugin to send messages to an audit instance. ServiceControl 6 will stop ingesting and forwarding Saga Audit to audit instances."); 
        
           await context.ForwardCurrentMessageTo(auditQueueName);

As the comment mentions, in v6, we want to remove that behavior. Evaluate if it's worth throwing an error.

Decided not to deprecate this "workaround" after all, as it provides a self-healing aspect to a misconfigured ServiceControl system. Instead we will elevate the log warning to a custom check that will be visible in ServicePulse in #4523.

	// TODO Forward saga audit messages and warn in ServiceControl 5, remove in 6
	log.WarnFormat("Configure the Saga Audit plugin to send messages to an audit instance. ServiceControl 6 will stop ingesting and forwarding Saga Audit to audit instances.");
	await context.ForwardCurrentMessageTo(auditQueueName);