FEATURE: Enable the new /about page for everyone (#29390)

This commit removes the feature flag for the new /about page, enabling it for all sites, and removes the code for old the /about page.

Internal topic: t/140413.

app/serializers/about_serializer.rb

@@ -55,18 +55,6 @@ class AboutSerializer < ApplicationSerializer
     SiteSetting.contact_email
   end
 
-  def include_extended_site_description?
-    render_redesigned_about_page?
-  end
-
-  def include_banner_image?
-    render_redesigned_about_page?
-  end
-
-  def include_site_creation_date?
-    render_redesigned_about_page?
-  end
-
   private
 
   def can_see_about_stats
@@ -76,10 +64,4 @@ class AboutSerializer < ApplicationSerializer
   def can_see_site_contact_details
     scope.can_see_site_contact_details?
   end
-
-  def render_redesigned_about_page?
-    return false if scope.anonymous?
-
-    scope.user.in_any_groups?(SiteSetting.experimental_redesigned_about_page_groups_map)
-  end
 end

app/serializers/current_user_serializer.rb

@@ -77,7 +77,6 @@ class CurrentUserSerializer < BasicUserSerializer
              :can_view_raw_email,
              :use_glimmer_topic_list?,
              :login_method,
-             :render_experimental_about_page,
              :has_unseen_features
 
   delegate :user_stat, to: :object, private: true
@@ -151,10 +150,6 @@ class CurrentUserSerializer < BasicUserSerializer
     object.staff?
   end
 
-  def render_experimental_about_page
-    object.in_any_groups?(SiteSetting.experimental_redesigned_about_page_groups_map)
-  end
-
   def can_post_anonymously
     SiteSetting.allow_anonymous_posting &&
       (is_anonymous || object.in_any_groups?(SiteSetting.anonymous_posting_allowed_groups_map))

app/serializers/site_serializer.rb

@@ -39,7 +39,6 @@ class SiteSerializer < ApplicationSerializer
     :markdown_additional_options,
     :hashtag_configurations,
     :hashtag_icons,
-    :displayed_about_plugin_stat_groups,
     :anonymous_default_navigation_menu_tags,
     :anonymous_sidebar_sections,
     :whispers_allowed_groups_names,
@@ -287,10 +286,6 @@ class SiteSerializer < ApplicationSerializer
     HashtagAutocompleteService.data_source_icon_map
   end
 
-  def displayed_about_plugin_stat_groups
-    About.displayed_plugin_stat_groups
-  end
-
   SIDEBAR_TOP_TAGS_TO_SHOW = 5
 
   def navigation_menu_site_top_tags