docs: fix x402 buyer examples

[vikions]

Description

Updates the x402 buyer examples to match the current Smart Accounts Kit and @metamask/x402 APIs.

The examples now:

• Read facilitator addresses from the correct facilitatorAddresses field.
• Use the supported redeemer parameter instead of passing execution rules directly.
• Let the delegation provider use the session account as the redelegation's from address.

These changes make the examples consistent with the published SDK behavior.

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Note

Low Risk
Documentation-only changes to example snippets; no runtime code, auth, or data paths are modified.

Overview
Updates the x402 buyer guides so copy-paste examples match the published Smart Accounts Kit and @metamask/x402 behavior.

In advanced-permissions, payment requirements and samples now use extra.facilitatorAddresses instead of facilitators, and requestExecutionPermissions passes facilitator allowlisting via the top-level redeemer option (documented as mapping to a redeemer rule) rather than a manual rules array.

In recurring-payments, createx402DelegationProvider no longer passes from: permission.from; the guide states the provider derives the open redelegation from address from the session account.

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[vercel]

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[shahbaz17]

cc @AyushBherwani1998