[Autofill Assistant] Removed unnecessary whitespace from onboarding layout.

Before: https://screenshot.googleplex.com/TT263fQ8F11.png
After: https://screenshot.googleplex.com/1scfPRBzvHn.png

Bug: 806868
Change-Id: Ida45b7b36526ebfb4e4abf18876106c47324fbe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1503313
Reviewed-by: Theresa <twellington@chromium.org>
Reviewed-by: Jordan Demeulenaere <jdemeulenaere@chromium.org>
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Cr-Commit-Position: refs/heads/master@{#638057}
3 files changed