MD Settings: Cleanup, remove non existing item-icon property from <iron-icon>.

chrome/browser/resources/settings/site_settings/site_details_permission.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-dropdown-menu/paper-dropdown-menu.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-listbox/paper-listbox.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="/i18n_setup.html">
 <link rel="import" href="/settings_shared_css.html">
 <link rel="import" href="/site_settings/constants.html">
 <link rel="import" href="/site_settings/site_settings_behavior.html">
@@ skipping 30 matching lines @@
         width: 100%;
       }
 
       .permission-list > paper-dropdown-menu::shadow > paper-menu-button {
         -webkit-margin-start: 11px;
         width: 100%;
       }
     </style>
     <div id="details" class="horizontal layout top" hidden>
       <div class="left-column">
-        <iron-icon icon="[[computeIconForContentCategory(category)]]"
-            item-icon></iron-icon>
+        <iron-icon icon="[[computeIconForContentCategory(category)]]">
+        </iron-icon>
       </div>
       <div class="flex right-column">
         <div class="permission-header">
           [[computeTitleForContentCategory(category)]]
         </div>
         <div class="permission-list">
           <paper-dropdown-menu vertical-align="auto">
             <paper-listbox id="permission" class="dropdown-content"
                 on-iron-activate="onPermissionMenuIronActivate_"
                 attr-for-selected="data-permission-value">
               <button id="allow" class="dropdown-item" role="option"
                   data-permission-value$="[[PermissionValues.ALLOW]]">
                 [[i18n_.allowAction]]
               </button>
               <button id="block" class="dropdown-item" role="option"
                   data-permission-value$="[[PermissionValues.BLOCK]]">
                  [[i18n_.blockAction]]
               </button>
             </paper-listbox>
           </paper-dropdown-menu>
         </div>
       </div>
     </div>
   </template>
   <script src="site_details_permission.js"></script>
 </dom-module>