Change joinmastodon.org to joinmastodon.org/#getting-started for sign up on another server (#10224)

app/views/about/_forms.html.haml

 - if @instance_presenter.open_registrations
   = render 'registration'
 - else
-  = link_to t('auth.register_elsewhere'), 'https://joinmastodon.org', class: 'button button-primary'
+  = link_to t('auth.register_elsewhere'), 'https://joinmastodon.org/#getting-started', class: 'button button-primary'
 
   .closed-registrations-message
     - if @instance_presenter.closed_registrations_message.blank?

app/views/about/_links.html.haml

@@ -11,6 +11,6 @@
         = link_to t('auth.login'), new_user_session_path, class: 'webapp-btn'
     %li= link_to t('about.about_this'), about_more_path
     %li
-      = link_to 'https://joinmastodon.org/' do
+      = link_to 'https://joinmastodon.org/#getting-started' do
         = "#{t('about.other_instances')}"
         %i.fa.fa-external-link{ style: 'padding-left: 5px;' }