Remove files for a modal that is no longer used.

Refs #4602
- The modal dialog that used to be shown when re-auth was
  needed in the editor has been replaced.

ghost/admin/controllers/modals/auth-failed-unsaved.js

@@ -1,33 +0,0 @@
-var AuthFailedUnsavedController = Ember.Controller.extend({
-    editorController: Ember.computed.alias('model'),
-
-    actions: {
-        confirmAccept: function () {
-            var editorController = this.get('editorController');
-
-            if (editorController) {
-                editorController.get('model').rollback();
-            }
-
-            window.onbeforeunload = null;
-
-            window.location = this.get('ghostPaths').adminRoot + '/signin/';
-        },
-
-        confirmReject: function () {
-        }
-    },
-
-    confirm: {
-        accept: {
-            text: 'Leave',
-            buttonClass: 'btn btn-red'
-        },
-        reject: {
-            text: 'Stay',
-            buttonClass: 'btn btn-default btn-minor'
-        }
-    }
-});
-
-export default AuthFailedUnsavedController;

ghost/admin/templates/modals/auth-failed-unsaved.hbs

@@ -1,8 +0,0 @@
-{{#gh-modal-dialog action="closeModal" showClose=true type="action" style="wide,centered" animation="fade"
-    title="Post NOT saved." confirm=confirm}}
-
-    <p>Hey there! Something has gone wrong and you have been logged out.  It looks like you have unsaved content that will be lost if you leave this page.</p>
-
-    <p>Copy your content somewhere safe before you go!</p>
-
-{{/gh-modal-dialog}}