winter sale: update banner interval.

Reset cookie and set the hide banner interval to 1 hour for the final
three hours of the sale.

app/javascript/src/javascripts/common.js

@@ -9,7 +9,7 @@ $(function() {
 
   $("#hide-promotion-notice").on("click.danbooru", function(e) {
     $("#promotion-notice").hide();
-    Cookie.put("hide_promotion_notice", "1", 1 * 18 * 60 * 60);
+    Cookie.put("hide_winter_sale_notice", "1", 1 * 60 * 60);
     Cookie.put("hide_upgrade_account_notice", "1", 7 * 24 * 60 * 60);
     e.preventDefault();
   });