Remove instance variables from helper usage (#24203)

app/lib/activitypub/dereferencer.rb

@@ -40,7 +40,7 @@ class ActivityPub::Dereferencer
   end
 
   def perform_request(uri, headers: nil)
-    return if invalid_origin?(uri)
+    return if non_matching_uri_hosts?(@permitted_origin, uri)
 
     req = Request.new(:get, uri)
 
@@ -57,13 +57,4 @@ class ActivityPub::Dereferencer
       end
     end
   end
-
-  def invalid_origin?(uri)
-    return true if unsupported_uri_scheme?(uri)
-
-    needle   = Addressable::URI.parse(uri).host
-    haystack = Addressable::URI.parse(@permitted_origin).host
-
-    !haystack.casecmp(needle).zero?
-  end
 end