[Test] Fix flaky test ManageSyncSettingsTest.testAdvancedSyncFlowBottomView()

The render mismatch for this test seems to be because of the scrollbar
beign shown when scrolling in recycler view. This cl hides the scrollbar
for the test to fix the test.

Bug: 1279777
Change-Id: I2974929f81154bd495d4f48cb9e4cbcf3aec5942
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3416636
Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Tanmoy Mollik <triploblastic@chromium.org>
Cr-Commit-Position: refs/heads/main@{#964045}