Settings[DICE]: fix sign-in button spacing

Bug: 813716
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I44ca92b701d1fc1140bdbfb577fb9cb0a5680219
Reviewed-on: https://chromium-review.googlesource.com/953972


Commit-Queue: Scott Chen <scottchen@chromium.org>
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#541952}(cherry picked from commit 72c62e41)
Reviewed-on: https://chromium-review.googlesource.com/958018


Reviewed-by: Scott Chen <scottchen@chromium.org>
Cr-Commit-Position: refs/branch-heads/3359@{#176}
Cr-Branched-From: 66afc5e5-refs/heads/master@{#540276}