Fix update payout scehdule end point

The updatePayoutSchedule endpoint currently requires both weekly_anchor and monthly_anchor fields, as shown in the screenshot. However, these fields should only be required when the interval is set to weekly or monthly, respectively. They are not always mandatory — for example, if the interval is set to daily, both fields can be omitted. Therefore, both weekly_anchor and monthly_anchor should be marked as optional and validated conditionally based on the interval value.