fix(transaction-pay-controller): clear stale rampsQuote on fiat quote failure

[amitabh94]

Explanation

When getFiatQuotes succeeds, it sets fiatPayment.rampsQuote on transaction state. On failure, the catch block previously only logged the error and returned an empty array — it never cleared rampsQuote. If a user had a prior successful quote and a later fetch failed (network blip, provider outage, etc.), the stale rampsQuote remained on state.

On mobile, useNoPayTokenQuotesAlert gates the fiat branch on !fiatPayment?.rampsQuote, so with a stale quote present the "No quotes" alert would never fire and the error was effectively swallowed.

This PR clears fiatPayment.rampsQuote in the getFiatQuotes catch block via TransactionPayController:updateFiatPayment, mirroring the symmetric success-path behavior that sets quoteError = undefined. A unit test verifies rampsQuote is undefined after RampsController:getQuotes throws.

References

• Related to mobile fiat quote error handling in useNoPayTokenQuotesAlert

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Low Risk
Small, targeted state cleanup on an existing error path in fiat quoting; behavior change is limited to failure cases and is covered by a new unit test.

Overview
When getFiatQuotes fails after logging and returning [], it now clears fiatPayment.rampsQuote via TransactionPayController:updateFiatPayment, so a prior successful ramps quote cannot linger and block fiat “no quotes” UI (e.g. mobile checks !fiatPayment?.rampsQuote).

A unit test asserts rampsQuote is undefined when RampsController:getQuotes throws; the package changelog records the fix.

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