Removed and disabled use of Ember.js function prototype extensions

no issue

- Function prototype extensions are being deprecated in Ember 3.11

ghost/admin/app/components/gh-canvas-header.js

@@ -4,10 +4,6 @@ import {run} from '@ember/runloop';
 export default Component.extend({
     tagName: '',
 
-    init() {
-        this._super(...arguments);
-    },
-
     actions: {
         initScrollWatch(element) {
             this._onScroll = run.bind(this, this.onScroll, element);

ghost/admin/app/mixins/validation-state.js

@@ -2,6 +2,7 @@ import Mixin from '@ember/object/mixin';
 import {A as emberA} from '@ember/array';
 import {isEmpty} from '@ember/utils';
 import {observer} from '@ember/object';
+import {on} from '@ember/object/evented';
 import {run} from '@ember/runloop';
 
 export default Mixin.create({
@@ -38,9 +39,9 @@ export default Mixin.create({
     },
 
     // eslint-disable-next-line ghost/ember/no-observers
-    hasErrorObserver: observer('errors.[]', 'property', 'hasValidated.[]', function () {
+    hasErrorObserver: on('init', observer('errors.[]', 'property', 'hasValidated.[]', function () {
         run.once(this, 'setHasError');
         // this.setHasError();
-    }).on('init')
+    }))
 
 });

ghost/admin/app/models/post.js

@@ -9,6 +9,7 @@ import {compare} from '@ember/utils';
 import {computed, observer} from '@ember/object';
 import {equal, filterBy} from '@ember/object/computed';
 import {isBlank} from '@ember/utils';
+import {on} from '@ember/object/evented';
 import {inject as service} from '@ember/service';
 
 // ember-cli-shims doesn't export these so we must get them manually
@@ -228,10 +229,10 @@ export default Model.extend(Comparable, ValidationEngine, {
 
     // TODO: is there a better way to handle this?
     // eslint-disable-next-line ghost/ember/no-observers
-    _setPublishedAtBlogTZ: observer('publishedAtUTC', 'settings.activeTimezone', function () {
+    _setPublishedAtBlogTZ: on('init', observer('publishedAtUTC', 'settings.activeTimezone', function () {
         let publishedAtUTC = this.publishedAtUTC;
         this._setPublishedAtBlogStrings(publishedAtUTC);
-    }).on('init'),
+    })),
 
     _setPublishedAtBlogStrings(momentDate) {
         if (momentDate) {

ghost/admin/config/environment.js

@@ -17,7 +17,7 @@ module.exports = function (environment) {
                 Date: false,
                 Array: true,
                 String: true,
-                Function: true
+                Function: false
             }
         },