Disable kReplaceSyncPromosWithSignInPromos in some failing tests

The flag is disabled explicitly for these tests to allow merging the
fieldtrial config to begin the experiments. The tests (most likely) do
not relate to an actual bug and only need adapting to the feature flag
being enabled. However, this can go afterwards and if needed,
cherry-picked to the release branch.

Bug: 444621374,444621383,444617960
Change-Id: If48b4706ae7d517707d1e7771745a79d2a27d9eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6975919
Commit-Queue: Ankush Singh <ankushkush@google.com>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1520069}