Removed @classic decorator from integrations controller

refs https://github.com/TryGhost/Ghost/issues/14101

- controller was already mostly up-to-date with Octane patterns
- removed unnecessary use of `@computed` and removed `@classic` decorator

ghost/admin/app/controllers/settings/integrations.js

@@ -1,31 +1,20 @@
-import classic from 'ember-classic-decorator';
-import {computed} from '@ember/object';
-import {inject as service} from '@ember/service';
-/* eslint-disable ghost/ember/alias-model-in-controller */
 import Controller from '@ember/controller';
+import {inject as service} from '@ember/service';
 import {task} from 'ember-concurrency';
 
-@classic
 export default class IntegrationsController extends Controller {
     @service settings;
     @service store;
     @service config;
 
-    _allIntegrations = null;
+    _allIntegrations = this.store.peekAll('integration');
 
-    init() {
-        super.init(...arguments);
-        this._allIntegrations = this.store.peekAll('integration');
-    }
-
-    @computed('config.hostSettings.limits')
     get zapierDisabled() {
         return this.config.get('hostSettings.limits.customIntegrations.disabled');
     }
 
     // filter over the live query so that the list is automatically updated
     // as integrations are added/removed
-    @computed('_allIntegrations.@each.{isNew,type}')
     get integrations() {
         return this._allIntegrations.reject((integration) => {
             return integration.isNew || integration.type !== 'custom';
@@ -35,10 +24,10 @@ export default class IntegrationsController extends Controller {
     // use ember-concurrency so that we can use the derived state to show
     // a spinner only in the integrations list and avoid delaying the whole
     // screen display
-    @task(function* () {
+    @task
+    *fetchIntegrations() {
         return yield this.store.findAll('integration');
-    })
-        fetchIntegrations;
+    }
 
     // used by individual integration routes' `model` hooks
     integrationModelHook(prop, value, route, transition) {