Fix status code 401 symbol usage in doc capture polling

[aduth]

Why: So that the server returns the expected status code (401) and doesn't error on an unrecognized status code

There doesn't appear to be much test coverage for this behavior, but I will plan to include some. I'd discovered this in the course of implementing tests for LG-3423 (dedicated controller for doc capture polling).

Reference: https://guides.rubyonrails.org/layouts_and_rendering.html#the-status-option

Because the front-end polling behavior checks only for 200 status code, it likely does not have a user-facing impact:

identity-idp/app/javascript/packs/doc_capture_polling.js

Lines 25 to 30 in d391f77

	request.onload = function () {
	// This endpoint renders a 202 for a pending request
	if (request.status === 200) {
	docCaptureComplete();
	}
	};

However, the use of an unrecognized status code symbol could produce errors in the server response.

[aduth]

I created this as a separate pull request since I'd worried this might have been a regression in recent revisions to document capture, though it appears this behavior has existed since the initial introduction of polling in March (#3646). If it's not proven to have been too problematic, this could wait for the refactoring work of LG-3423?

[zachmargolis]

There doesn't appear to be much test coverage for this behavior, but I will plan to include some

Good catch, thanks for tests --- very surprised we didn't catch this sooner 😬

[aduth]

This fix is absorbed into #4293.

We could still choose to cherry-pick this change if we decide to try to patch RC 120.