[Due for payment 2026-06-09] [IOURequestStepScan Decomposition] chore: remove dead scan MoneyRequest path + hooks + tests

[cristipaval]

Held on #89384

Part of IOURequestStepScan Decomposition Plan — see rinej's split design comment.

Parent: #85583

Problem

After variants own scan behavior, the old centralized participant/navigation hook path and monolith hooks become dead code and maintenance noise.

Solution

Delete handleMoneyRequestStepScanParticipants and related types from MoneyRequest.ts, remove useReceiptScan and useMobileReceiptScan, and drop or rewrite the tests that only covered that stack, as listed in the plan.

Issue Owner

Current Issue Owner: @mallenexpensify

[melvin-bot]

@bernhardoj Uh oh! This issue is overdue by 2 days. Don't forget to update your issues!

[cristipaval]

Held on #89384

[melvin-bot]

@rinej Uh oh! This issue is overdue by 2 days. Don't forget to update your issues!

[cristipaval]

still held