Remove outdated comment of ActiveRecord's spawn method. [ci-skip]

[simi]

Per my findings, this method is not overridden anymore.

[kamipo]

Duplicated with #41168.

[simi]

Ahh, thanks for info @kamipo and sorry for wasting your time :(

If I understand it well, it is actually delegated to scope and that calls ActiveRecord::SpawnMethods#spawn again. Per the explicit comment I would expect custom spawn method implemented in Associations::CollectionProxy. It seems I'm not the only one confused by this comment. Would it be welcomed to at least reword the comment to make it easier to follow? Any ideas?

[kamipo]

Originally this private method existed just to emulate the equivalent behavior of a relation.clone on a collection proxy for internal use, but now exists for more complex purposes. I prefer to just remove it rather than comment on the exact purpose of this private method.