[MD settings] remove unused categorySelected property

This CL removes an unused property to make the code cleaner.

BUG=None
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2593453002
Cr-Commit-Position: refs/heads/master@{#439868}

chrome/browser/resources/settings/privacy_page/privacy_page.html

@@ -197,8 +197,7 @@
             associated-control="[[$$('#site-settings-subpage-trigger')]]"
             id="site-settings"
             page-title="[[siteSettingsPageTitle_()]]">
-          <settings-site-settings-page category-selected="{{categorySelected}}">
-          </settings-site-settings-page>
+          <settings-site-settings-page></settings-site-settings-page>
         </settings-subpage>
       </template>
 

chrome/browser/resources/settings/site_settings_page/site_settings_page.js

@@ -20,14 +20,6 @@ Polymer({
         return loadTimeData.getBoolean('enableSiteSettings');
       },
     },
-
-    /**
-     * The category selected by the user.
-     */
-    categorySelected: {
-      type: String,
-      notify: true,
-    },
   },
 
   ready: function() {