chrome://bookmarks: increase padding on managed UI icon

8px => 12px to match the mocks.

Change-Id: I801542001f7c2d73da62e47870c856509097fda4
Reviewed-on: https://chromium-review.googlesource.com/c/1425479
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Reviewed-by: Dan Beam (slow until 1/29) <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626121}

chrome/browser/resources/bookmarks/app.html

@@ -76,6 +76,7 @@
       }
 
       managed-footnote {
+        --managed-footnote-icon-padding: 12px;
         flex: 0;
         padding-bottom: 24px;
         padding-top: 24px;