Revert "ChromeVox: Enable mv3 spoken feedback tests"

This reverts commit d9b983a656f7d4ca5905043fbc08b038f8cc26ad.

Reason for revert: newly added tests are flaky 
https://ci.chromium.org/ui/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests

Original change's description:
> ChromeVox: Enable mv3 spoken feedback tests
>
> Bug: 388867840
> Change-Id: I38aff6d672dd0371290a582352416c59ec58661c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6875564
> Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
> Reviewed-by: Jesulayomi Kupoluyi <lkupo@google.com>
> Cr-Commit-Position: refs/heads/main@{#1522893}

Bug: 388867840
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I86c9d58dd3c45acf7561a0cd3e5186bab6c1da02
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6999514
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Lingqi Chi <lingqi@chromium.org>
Auto-Submit: Lingqi Chi <lingqi@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1523320}