Revert "[FedCM] Make title label focusable with accessibility enabled"

This reverts commit a2c84e24d92a8b25c3631b5ec220be1710b1806c.

Reason for revert: requested by a11y reviewer

Original change's description:
> [FedCM] Make title label focusable with accessibility enabled
>
> This lets us have more consistent behavior across OS and dialogs since
> we can now focus on the title label when the dialog is shown.
>
> Demo: https://issues.chromium.org/issues/354240721#comment4
>
> Fixed: 354240721
> Change-Id: I1e534b42aa86fb1dcc070066da0ae68a7b7e8b32
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5735020
> Reviewed-by: Yi Gu <yigu@chromium.org>
> Commit-Queue: Nicolás Peña <npm@chromium.org>
> Auto-Submit: Nicolás Peña <npm@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1332486}

Change-Id: I113e9ce7b941ec873cb1689cf00750127a714245
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5749570
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Nicolás Peña <npm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1335077}