Resolve remote accounts when mentioned even if they are already known (#5539)

This commit reduces the risk of not having up-to-date public key or protocol
information for a remote account, which is required to deliver toots
(especially direct messages).

app/services/process_mentions_service.rb

@@ -11,16 +11,11 @@ class ProcessMentionsService < BaseService
     return unless status.local?
 
     status.text.scan(Account::MENTION_RE).each do |match|
-      username, domain  = match.first.split('@')
-      mentioned_account = Account.find_remote(username, domain)
-
-      if mentioned_account.nil? && !domain.nil?
       begin
         mentioned_account = resolve_remote_account_service.call(match.first.to_s)
       rescue Goldfinger::Error, HTTP::Error
         mentioned_account = nil
       end
-      end
 
       next if mentioned_account.nil?