Fix TS error

[luacmartins]

Problem

We have @ts-expect-error TODO: Remove this once TestHelper (https://github.com/Expensify/App/issues/25318) is migrated to TypeScript in many places throughout our tests -- 135 occurrences as of today, example. We should fix the TS error and remove that comment.

[melvin-bot]

Triggered auto assignment to @lschurr (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[luacmartins]

Closing this in favor of #39130