Remove Salmon and PubSubHubbub (#11205)

* Remove Salmon and PubSubHubbub endpoints

* Add error when trying to follow OStatus accounts

* Fix new accounts not being created in ResolveAccountService

app/views/admin/subscriptions/_subscription.html.haml

@@ -1,18 +0,0 @@
-%tr
-  %td
-    %samp= subscription.account.acct
-  %td
-    %samp= subscription.callback_url
-  %td
-    - if subscription.confirmed?
-      %i.fa.fa-check
-  %td{ style: "color: #{subscription.expired? ? 'red' : 'inherit'};" }
-    %time.time-ago{ datetime: subscription.expires_at.iso8601, title: l(subscription.expires_at) }
-      = precede subscription.expired? ? '-' : '' do
-        = time_ago_in_words(subscription.expires_at)
-  %td
-    - if subscription.last_successful_delivery_at?
-      %time.formatted{ datetime: subscription.last_successful_delivery_at.iso8601, title: l(subscription.last_successful_delivery_at) }
-        = l subscription.last_successful_delivery_at
-    - else
-      %i.fa.fa-times

app/views/admin/subscriptions/index.html.haml

@@ -1,16 +0,0 @@
-- content_for :page_title do
-  = t('admin.subscriptions.title')
-
-.table-wrapper
-  %table.table
-    %thead
-      %tr
-        %th= t('admin.subscriptions.topic')
-        %th= t('admin.subscriptions.callback_url')
-        %th= t('admin.subscriptions.confirmed')
-        %th= t('admin.subscriptions.expires_in')
-        %th= t('admin.subscriptions.last_delivery')
-    %tbody
-      = render @subscriptions
-
-= paginate @subscriptions