[Clean up] Fix style guide nits in chrome/browser/resources/options2.

chrome/browser/resources/options2/import_data_overlay.css

+/* Copyright (c) 2012 The Chromium Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file. */
+
 #import-from-div {
   margin-bottom: 20px;
 }
 
 #import-checkboxes > div:not(:first-child) {
   -webkit-padding-start: 8px;
   margin: 5px 0;
 }
 
 #import-throbber {
   margin: 4px 10px;
   vertical-align: middle;
   visibility: hidden;
 }
 
 #import-success-header {
   font-size: 1.2em;
 }
 
 #import-success-image {
+  margin: 20px;
   text-align: center;
-  margin: 20px;
 }