Added troubleshooting instructions for Attempt_Exceed_Limitation error

What does this MR do and why?

Customers could encounter Attempt_Exceed_Limitation - Attempt exceed the limitation, refresh page to try again. error when going through the purchase flow. This error is related to Zuora's rate limiting configuration, to prevent abuse of the credit card form.

This MR is adding an explanation and troubleshooting instructions.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.