Change "What's New" dropdown item URL

part of: https://gitlab.com/gitlab-org/growth/product/-/issues/1487

ee/app/views/layouts/header/_whats_new_dropdown_item.html.haml

 - if show_whats_new_dropdown_item?
   %li
-    = link_to _("See what's new at GitLab"), "#{promo_url}/releases/categories/releases/", target: '_blank', rel: 'noopener noreferrer', data: { track_event: 'click_whats_new', track_property: 'question_menu' }
+    = link_to _("See what's new at GitLab"), "#{promo_url}/releases/gitlab-com/", target: '_blank', rel: 'noopener noreferrer', data: { track_event: 'click_whats_new', track_property: 'question_menu' }

ee/changelogs/unreleased/jswain_change_whats_new_url.yml

+---
+title: Change 'Whats New' dropdown item url
+merge_request: 30198
+author:
+type: changed