feat!: Drop the legacy studio updates page. (#37544)

Remove the legacy studio updates page and its related artifacts. They
have been replaced by API and a new UI in the authoring MFE.

This cleanup is a part of https://github.com/openedx/edx-platform/issues/36108

BREAKING CHANGE: The 'legacy_studio.updates' waffle flag will no longer
be respected. The system will behave as if the flag is set to false
permanently.

cms/templates/widgets/header.html

@@ -46,7 +46,6 @@
                 certificates_url = reverse('certificates_list_handler', kwargs={'course_key_string': str(course_key)})
             checklists_url = reverse('checklists_handler', kwargs={'course_key_string': str(course_key)})
             pages_and_resources_mfe_enabled = ENABLE_PAGES_AND_RESOURCES_MICROFRONTEND.is_enabled(context_course.id)
-            updates_mfe_enabled = toggles.use_new_updates_page(context_course.id)
             video_upload_mfe_enabled = toggles.use_new_video_uploads_page(context_course.id)
             schedule_details_mfe_enabled = toggles.use_new_schedule_details_page(context_course.id)
             grading_mfe_enabled = toggles.use_new_grading_page(context_course.id)
@@ -83,16 +82,9 @@
                     <a href="${get_course_libraries_url(course_key)}">${_("Libraries")}</a>
                   </li>
                   % endif
-                  % if not updates_mfe_enabled:
-                  <li class="nav-item nav-course-courseware-updates">
-                    <a href="${course_info_url}">${_("Updates")}</a>
-                  </li>
-                  % endif
-                  % if updates_mfe_enabled:
                   <li class="nav-item nav-course-courseware-updates">
                     <a href="${get_updates_url(course_key)}">${_("Updates")}</a>
                   </li>
-                  % endif
                   % if not pages_and_resources_mfe_enabled:
                   <li class="nav-item nav-course-courseware-pages">
                     <a href="${tabs_url}">${_("Pages")}</a>