reverting add readonly to site settings

see this commit for more details:

2ffddfb32c (commitcomment-22480952)

app/assets/javascripts/admin/controllers/admin-site-settings.js.es6

@@ -1,5 +1,4 @@
 import debounce from 'discourse/lib/debounce';
-import { ajax } from 'discourse/lib/ajax';
 
 export default Ember.Controller.extend({
   filter: null,
@@ -71,36 +70,7 @@ export default Ember.Controller.extend({
 
     toggleMenu() {
       $('.admin-detail').toggleClass('mobile-closed mobile-open');
-    },
-
-    toggleReadOnlyMode() {
-      var self = this;
-      if (!this.site.get("isReadOnly")) {
-        bootbox.confirm(
-          I18n.t("admin.backups.read_only.enable.confirm"),
-          I18n.t("no_value"),
-          I18n.t("yes_value"),
-          function(confirmed) {
-            if (confirmed) {
-              Discourse.User.currentProp("hideReadOnlyAlert", true);
-              self._toggleReadOnlyMode(true);
-            }
-          }
-        );
-      } else {
-        this._toggleReadOnlyMode(false);
-      }
     }
-  },
-
-  _toggleReadOnlyMode(enable) {
-    var site = this.site;
-    ajax("/admin/backups/readonly", {
-      type: "PUT",
-      data: { enable: enable }
-    }).then(() => {
-      site.set("isReadOnly", enable);
-    });
   }
 
 });

app/assets/javascripts/admin/templates/site-settings.hbs

@@ -1,10 +1,5 @@
 <div class='admin-controls'>
   <div class='search controls'>
-    {{#if site.isReadOnly}}
-      {{d-button icon="eye" action="toggleReadOnlyMode" disabled=status.isOperationRunning title="admin.backups.read_only.disable.title" label="admin.backups.read_only.disable.label"}}
-    {{else}}
-      {{d-button icon="eye" action="toggleReadOnlyMode" disabled=status.isOperationRunning title="admin.backups.read_only.enable.title" label="admin.backups.read_only.enable.label"}}
-    {{/if}}
     <label>
       {{input type="checkbox" checked=onlyOverridden}}
       {{i18n 'admin.site_settings.show_overriden'}}