[Bug] schedule update removing cron if not explicitly included

[billrich2001]

What are you really trying to do?

Update a schedule.

Describe the bug

The following command results in the removal of the existing cron configuration from the schedule:

temporal schedule update 
--env prod 
--schedule-id "Start Invoice Processing - Daily at 09:00 UTC (01:00 PST / 02:00 PDT)" 
--overlap-policy AllowAll 
--type start-invoice-processing 
--task-queue invoices-queue

Adding the --cron parameter resolves the issue and preserves the schedule configuration:
--cron "0 9 * * *"