Explain walkdir docstring second example.

[nathanrboyer]

This is a follow-up documentation PR to #55476. I believe the second example in the walkdir docstring is still unintuitive since the result changes each time. I attempted a simple explanation, but I don't really know what I'm talking about. Hopefully someone else can explain what is happening better. Some additional discussion in this Discourse post.

[LilithHafner]

walkdir returns a stateful iterator (much like Iterators.Stateful). The relevant paragraph from the Stateful docstring that explains this best to me is

  `Stateful` provides the regular iterator interface. Like other mutable
  iterators (e.g. `Base.Channel`), if iteration is stopped early (e.g. by a
  `break` in a `for` loop), iteration can be resumed from the same spot by
  continuing to iterate over the same iterator object (in contrast, an
  immutable iterator would restart from the beginning).

[LilithHafner]

LGTM! Does this make sense & seem ready to merge to you, too?

[nathanrboyer]

Yep! It gives the user an expectation for the behavior and a link to dig deeper if desired. Thanks!

[nathanrboyer]

As a funny aside, I spent the last two PRs thinking "LGTM" meant "Let's get to merge" and didn't bother looking it up until just now, but that did result in a pretty fast turnaround for these PRs 😆

[LilithHafner]

To me, "LGTM"/"looks good to me" means "I would merge this as is".

I'm also a fan of merging PRs reasonably quickly because PRs that sit open for long periods of time become stale, both technically and in the minds of authors and reviewers, which makes them harder to progress on.