Revert "[Multipaste] Speak a11y announcement when delete button is focused"

This reverts commit a2c9272d.

Reason for revert: suspect this cl causes build failure https://ci.chromium.org/p/chromium/builders/ci/Linux%20ChromiumOS%20MSan%20Tests/21195

Original change's description:
> [Multipaste] Speak a11y announcement when delete button is focused
>
> This CL does two things:
> (1) Ignore the MenuItemView instance in accessibility events handling.
> Then we can customize accessibility behaviors of the multipaste menu
> in ClipboardHistoryItemView class.
>
> (2) When the delete button gets the pseudo focus, the accessibility
> side is notified.
>
> Bug: 1145773
> Change-Id: Ibd73b04637b89cc8200ca2f74721a10a44e857c4
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2513502


> Reviewed-by: Alex Newcomer <newcomer@chromium.org>
> Commit-Queue: Andrew Xu <andrewxu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#824561}

TBR=newcomer@chromium.org,andrewxu@chromium.org

Change-Id: I999c30afd42fa4c703f506a536fd736bcbfb48df
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1146255
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2523237


Reviewed-by: Tina Wang <tinazwang@chromium.org>
Commit-Queue: Tina Wang <tinazwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#824885}