send_later: Wildcard mention throwing error on send later.

It was throwing error while schudiling a message having wildcard mention,
because the function `open_send_later_menu` was using param instance to track down
interval, but the parametere instance was not passed from when it was
called from warning banner action. This commit removes the instance
param as it is of no use, and uses a variable to track interval.

web/src/popover_menus.js

@@ -239,7 +239,7 @@ function set_compose_box_schedule(element) {
     return selected_send_at_time;
 }
 
-export function open_send_later_menu(instance) {
+export function open_send_later_menu() {
     if (!compose_validate.validate(true)) {
         return;
     }
@@ -248,11 +248,12 @@ export function open_send_later_menu(instance) {
     const date = new Date();
     const filtered_send_opts = scheduled_messages.get_filtered_send_opts(date);
     $("body").append(render_send_later_modal(filtered_send_opts));
+    let interval;
 
     overlays.open_modal("send_later_modal", {
         autoremove: true,
         on_show() {
-            instance._interval = setInterval(
+            interval = setInterval(
                 scheduled_messages.update_send_later_options,
                 scheduled_messages.SCHEDULING_MODAL_UPDATE_INTERVAL_IN_MILLISECONDS,
             );
@@ -312,7 +313,7 @@ export function open_send_later_menu(instance) {
             $send_later_modal_overlay.trigger("focus");
         },
         on_hide() {
-            clearInterval(instance._interval);
+            clearInterval(interval);
         },
     });
 }
@@ -905,7 +906,7 @@ export function initialize() {
                 const send_at_timestamp = get_selected_send_later_timestamp();
                 do_schedule_message(send_at_timestamp);
             });
-            $popper.one("click", ".open_send_later_modal", () => open_send_later_menu(instance));
+            $popper.one("click", ".open_send_later_modal", open_send_later_menu);
         },
         onHidden(instance) {
             instance.destroy();