Release testing instructions for WC Payments 6.8.0

Fix not allowed page when clicking Set up WooPayments from Core and account is already onboarded

• Initiate the onboarding process and complete it fully.
• Check that the account is complete on the payments overview page.
• Go to WooCommerce → Home and find Set up WooPayments task, it should be marked as complete.
• Click on it and wait a little bit.
• Should redirect to the payments overview page.