Fix logging.Handler.lock can't be None

[kbaikov]

Fixes: #13381

[AlexWaygood]

@JelleZijlstra's comment in #13381 (comment) suggested that we shouldn't make this change, and that there was nothing to be done here

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[kbaikov]

@AlexWaygood I think he just misunderstood the issue, because the issue title has a question mark.
It took me 2 reads to notice it :)

Or perhaps you are right.

[kbaikov]

Then should the issue #13381 be just closed?

[JelleZijlstra]

My comment would imply that the issue should be closed, yes. But I'm happy to defer to others' opinions if someone disagrees.