Change message of public timeline for local only (#12224)

app/views/public_timelines/show.html.haml

@@ -7,7 +7,11 @@
 
 .page-header
   %h1= t('about.see_whats_happening')
-  %p= t('about.browse_public_posts')
+
+  - if Setting.show_known_fediverse_at_about_page
+    %p= t('about.browse_public_posts')
+  - else
+    %p= t('about.browse_local_posts')
 
 #mastodon-timeline{ data: { props: Oj.dump(default_props) }}
 #modal-container