Fix AccessibilityHearingAidPreferenceControllerTest

**Root cause**
When adding a feature flag on showing different hearing aid page on
 click, the tests were not executed because they were marked as @Ignore.

In order to execute the test, we need to turn the feature flag off, so that the test run in the same scenario where the feature flag was not introduced.

Bug: 279082331
Test: atest AccessibilityHearingAidPreferenceControllerTest
Change-Id: If11ac40a7ea3926578992f7c0577e7cbb1bb3273