Added auto save to newsletters toggle

refs https://github.com/TryGhost/Team/issues/1639

- When enabling/disabling newsletters, the change is saved automatically

ghost/admin/app/components/settings/newsletters.js

@@ -85,6 +85,11 @@ export default class Newsletters extends Component {
         }
 
         this.recipientsSelectValue = this._getDerivedRecipientsSelectValue();
+
+        // Force a save when the toggle is changed
+        // this is required
+        // eslint-disable-next-line no-console
+        this.settings.save().catch(console.error);
     }
 
     @action