Shimless: Convert onboarding_choose_wp_disable_method_page_test.js to ts

- Fix all ts errors and use ts styling.

Test: browser_tests --gtest_filter=ShimlessRmaApp.OnboardingChooseWpDisableMethodPage
Bug: b:315002705
Change-Id: I6da0d08caf7fc37560c5a4dbae7012fee021bbc2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5405479


Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Reviewed-by: Ashley Prasad <ashleydp@google.com>
Cr-Commit-Position: refs/heads/main@{#1280505}