CR-3173: Remove flaky test -- various failure modes, 30-50% pass rate (#437)
CR-3173: Remove flaky test -- various failure modes, 30-50% pass rate (#437)

Following flaky test process. Example failures:

- "bok_choy.promise.BrokenPromise: Promise not satisfied: Add xblock
  button is visible."
- "bok_choy.promise.BrokenPromise: Promise not satisfied: Executing
  BrowserQuery(css='.add-xblock-component-button[data-type="advanced"]').map(click())"
edx/edx-e2e-tests,edx/edx-e2e-tests