Correct caption of 'Make Visible' button

The variable 'visible' is also used for toggling the admin menu visibility,
so it is always true when the visibility toggle is shown. Hence, it's caption
is always 'Make Invisible', even when the topic already is invisible.

app/assets/javascripts/discourse/controllers/topic_admin_menu_controller.js

@@ -7,15 +7,15 @@
   @module Discourse
 **/
 Discourse.TopicAdminMenuController = Discourse.ObjectController.extend({
-  visible: false,
+  menuVisible: false,
   needs: ['modal'],
 
   show: function() {
-    this.set('visible', true);
+    this.set('menuVisible', true);
   },
 
   hide: function() {
-    this.set('visible', false);
+    this.set('menuVisible', false);
   }
 
 });

app/assets/javascripts/discourse/templates/topic_admin_menu.js.handlebars

@@ -1,4 +1,4 @@
-{{#if visible}}
+{{#if menuVisible}}
   <div class="topic-admin-menu">
     <h3>{{i18n admin_title}}</h3>