[Cashtab] Streamline loading conditions in flaky test

Summary: Seen this fail in CI. Remove the numerous conditional loading checks and instead use only a single async check for the condition we are specifically testing in this test.

Test Plan: npm test

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17876