MD Settings: Remove usage of deprecated iron-flex-layout.html, for CrOS.

chrome/browser/resources/settings/people_page/users_page.html

 <link rel="import" href="chrome://resources/html/action_link.html">
 <link rel="import" href="chrome://resources/html/action_link_css.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../settings_shared_css.html">
 <link rel="import" href="user_list.html">
 <link rel="import" href="users_add_user_dialog.html">
 
 <dom-module id="settings-users-page">
   <template>
     <style include="settings-shared action-link">
       .settings-box:first-of-type {
         border-top: none;
       }
 
       #add-user-button {
         /* Add user button must be lined up with the start of users' names. */
         -webkit-margin-start: var(--settings-box-row-indent);
       }
+
+      .block {
+        display: block;
+      }
     </style>
     <template is="dom-if" if="[[isWhitelistManaged_]]">
       <div class="settings-box">$i18n{settingsManagedLabel}</div>
     </template>
     <template is="dom-if" if="[[!isWhitelistManaged_]]">
       <template is="dom-if" if="[[!isOwner_]]">
         <div class="settings-box">$i18n{usersModifiedByOwnerLabel}</div>
       </template>
     </template>
     <div class="settings-box block">
@@ skipping 32 matching lines @@
           $i18n{addUsers}
         </a>
       </div>
     </div>
     <settings-users-add-user-dialog id="addUserDialog"
         on-close="onAddUserDialogClose_">
     </settings-users-add-user-dialog>
   </template>
   <script src="users_page.js"></script>
 </dom-module>