notify_iter docs state expired elements are removed before creating iterator

[That3Percent]

Describe the bug
notify_iter docs state: "Also removes expired elements before creating the iterator.", which appears to have been copy-pasted from the docs of fn iter.

This conflicts with the implementation, which removes elements as they are encountered during iteration.

I expect that it is the docs that are incorrect and not the implementation.

This created an issue for a project I work on where the cache grew without bound, because it was relying on that call to expire entries from the cache without iterating.