Remove remaining type comments in favour of PEP 526 annotations

[AlexWaygood]

A followup to #13427. Unlike #13427, this PR was prepared manually.

[hauntsaninja]

That PR also introduced a couple changes where code become unidiomatic for instance variables:

x = None  # type: int

should become x: int, not x: int = None.

Relatedly, I think the code in misc isn't getting type checked, and maybe it should

[AlexWaygood]

That PR also introduced a couple changes where code become unidiomatic for instance variables

I'll take a look and fix those, thanks.

Relatedly, I think the code in misc isn't getting type checked, and maybe it should

+1

[AlexWaygood]

That PR also introduced a couple changes where code become unidiomatic for instance variables:

Have you got any examples in mind? The only one I can immediately see that looks quite suspicious is this one: 23ee1e7#diff-e9eee110f5e0a0409c615a1beb8092eb551338a98e6e20948361ebb44e611c16R25

And that's already been fixed in #13452

[github-actions]

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