forum: do not update lastSeenAt when modifying discloseOnline preference

This value is immediately set in the backend again, so apart from causing visual glitches, it is useless as the preference doesn't prevent admins from seeing your last seen at time

js/src/common/components/LinkButton.tsx

@@ -1,8 +1,8 @@
 import Button, { ButtonProps } from './Button';
 
 interface LinkButtonProps extends ButtonProps {
-    active: boolean;
-    oncreate: Function;
+    active?: boolean;
+    oncreate?: Function;
     href?: string;
 }
 

js/src/common/models/User.ts

@@ -101,7 +101,7 @@ export default class User extends Model {
     /**
      * Update the user's preferences.
      */
-    savePreferences(newPreferences: object): Promise<User> {
+    savePreferences(newPreferences: UserPreferences): Promise<User> {
         const preferences = this.preferences();
 
         Object.assign(preferences, newPreferences);

js/src/forum/components/SettingsPage.tsx

@@ -122,10 +122,7 @@ export default class SettingsPage extends UserPage {
             Switch.component({
                 children: app.translator.trans('core.forum.settings.privacy_disclose_online_label'),
                 state: this.user.preferences().discloseOnline,
-                onchange: (value, component) => {
-                    this.user.pushAttributes({ lastSeenAt: null });
-                    this.preferenceSaver('discloseOnline')(value, component);
-                },
+                onchange: (value, component) => this.preferenceSaver('discloseOnline')(value, component),
             })
         );