Settings WebUI: certificate-list, add spacing between buttons

Bug: 963845
Change-Id: I7585fb60aa7582e39af0beb38651a4fcefb48623
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1613750Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Commit-Queue: Esmael El-Moslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661071}

ui/webui/resources/cr_components/certificate_manager/certificate_list.html

@@ -19,6 +19,11 @@
         min-height: 48px;
         padding: 0 20px;
       }
+
+      /* TODO(aee): add platform conditional after crbug/964506 is fixed. */
+      #importAndBind {
+        margin-inline-start: 8px;
+      }
     </style>
     <div class="button-box">
       <span class="flex">