Revert "[Read Aloud] Fix toast contrast"

This reverts commit 8ac29b95.

Reason for revert: Toast not showing due to shadow root error

Original change's description:
> [Read Aloud] Fix toast contrast
>
> Show the language downloaded toast in front of language menu dialog
> when it's open so it does not get partially blocked
> by the dialog scrim.
>
> This is done by adding a cr-toast element inside the dialog and show that one when the dialog is open.
>
> https://screenshot.googleplex.com/6pxGi6Uv8ymYkjq
>
> Bug: 343966559
> Change-Id: I9dec7bc2a23553c28bce72ec14104c67cd9dcd99
> Fixed: 343966559
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5607344


> Reviewed-by: Lauren Winston <lwinston@google.com>
> Commit-Queue: Lauren Winston <lwinston@google.com>
> Reviewed-by: Eitan Goldberger <eitang@google.com>
> Cr-Commit-Position: refs/heads/main@{#1312820}

Bug: 343966559
Change-Id: I21a7dd0f0297f624e654a3817b2ef2835328082d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5617444
Commit-Queue: Lauren Winston <lwinston@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1313054}