To delete your payment method (credit card, debit card, etc) from the Stripe billing portal. Follow the steps below.
Go to Settings > Billing & Payments > Manage Subscription:
Under the Payment Methods section, select the three dot menu to the right of the payment method and select Delete:
Your payment method is deleted.
Note, if you have an active subscription using the payment method, it cannot be deleted. You will need to cancel the subscription first.