Fix flakey JavaScript spec for async navigate

[aduth]

🛠 Summary of changes

Improves reliability of JavaScript tests where a user is navigated after selecting a post office in the in-person proofing flow.

Example failure: https://gitlab.login.gov/lg/identity-idp/-/jobs/985447 (via #9972)

The behavior for redirecting after making a selection occurs only after a network request has finished, which may not be instantaneous.

identity-idp/app/javascript/packages/document-capture/components/in-person-location-post-office-search-step.tsx

Lines 58 to 61 in a68df92

	await request(locationsURL, {
	json: selected,
	method: 'PUT',
	});

📜 Testing Plan

yarn mocha app/javascript/packages/document-capture/components/in-person-location-post-office-search-step.spec.tsx app/javascript/packages/document-capture/components/in-person-location-full-address-entry-post-office-search-step.spec.tsx