Clarify comment [ci skip]

activestorage/app/models/active_storage/variant.rb

@@ -65,7 +65,7 @@ def service_url(expires_in: service.url_expires_in, disposition: :inline)
     service.url key, expires_in: expires_in, disposition: disposition, filename: blob.filename, content_type: blob.content_type
   end
 
-  # Returns the receiving variant. Allows ActiveStorage::Variant and ActiveStorage::Preview instances to be duck-typed.
+  # Returns the receiving variant. Allows ActiveStorage::Variant and ActiveStorage::Preview instances to be used interchangeably.
   def image
     self
   end