Check preferences sync user toggle for syncing autosignin setting

No effective change.

PRIORITY_PREFERENCES data type is tied to the preferences user toggle.
If the toggle is off, the data type will not be active. With
`kSyncSupportAlwaysSyncingPriorityPreferences` feature, we are changing
this behavior and PRIORITY_PREFERENCES is decoupled from the user toggle
and is always active. The callsites should instead check for the
preferences sync user toggle.

Bug: 412602018
Change-Id: I954fdc2007675bc5a4cf5c9ba5de6a83c37a7b3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6494468
Reviewed-by: Mohamed Amir Yosef <mamir@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Auto-Submit: Ankush Singh <ankushkush@google.com>
Cr-Commit-Position: refs/heads/main@{#1452686}