[unified-consent] Fix button spacing in confirmation dialog

Bug: 872642
Change-Id: I1b067bb722650752c00c43d0b77308214ae50fd1
Reviewed-on: https://chromium-review.googlesource.com/c/1333655Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Thomas Tangl <tangltom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607757}

chrome/browser/resources/signin/dice_sync_confirmation/sync_confirmation_app.html

@@ -37,13 +37,13 @@
       }
 
       paper-button:not(.action-button) {
-        margin-inline-start: 16px;
+        margin-inline-start: 8px;
       }
 
 <if expr="is_macosx or is_linux">
       /* This works together with the button-flip in signin-dialog-shared. */
       paper-button:not(.action-button) {
-        margin-inline-end: 16px;
+        margin-inline-end: 8px;
         margin-inline-start: 0;
       }
 </if>