settings: Use form element in handler for notification settings.

Notification settings uses '.on("change", "input, select")' to
handle changes to all types of input elements. But for realm-level
settings page, both display and notification settings have the
same container unlike the user-level settings, so we use inner
form element ".notification-settings-form" such that this handler
is for changing input of notification settings and not display
settings.

static/js/settings_notifications.js

@@ -81,7 +81,7 @@ export function set_up() {
     const container = $("#user-notification-settings");
     const patch_url = "/json/settings";
     const settings_object = user_settings;
-    container.on("change", "input, select", function (e) {
+    container.find(".notification-settings-form").on("change", "input, select", function (e) {
         e.preventDefault();
         e.stopPropagation();
         const input_elem = $(e.currentTarget);