removed fields which are not sent in API

[soularchx86]

Why:
partners were relying on fields that the code does not send (causing 500s).
What I changed:
Deprecated or unused fields have been removed across multiple event types (refund, payment failure, collection failure, and fetch failure). These removals include fields such as billAmount, billId, dueDate, txnId, and similar payment or bill identifiers. All affected examples and field tables have been updated accordingly to reflect the streamlined payload structure.
Files changed:
setudocs/docs/content/payments/billpay/pre-built-screens/webhooks.mdx
setudocs/docs/content/payments/billpay/v1/pre-built-screens/webhooks.mdx
Impact: documentation now matches UserEventCallbackConsumer behaviour, partners should stop relying on absent fields and handle updated details instead.

[github-actions]

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