Remove #type: comments for attributes.

[ssbr]

A lot of classes in refex predate the attrs type argument, so that they look like this:

@attr.s(...)
class Foo(...)
  x = attr.ib(...)  # type: SomeTypeHere

The new form is:

@attr.s(...)
class Foo(...)
  x = attr.ib(..., type=SomeTypeHere)

Benefits of the new form:

1. shows up in documentation.
2. better-supported by tools
3. formats way better when you need to break across lines etc.

It might be a neat thing to do to, well, automate this via refex and apply it to refex itself. ;) It's a nontrivial matcher, because it involves editing (removing) a comment and editing the arguments to a function, which makes it useful as a demonstration of how to do nontrivial things with Refex. Since pretty much the only time anyone wants to use Refex is when it's something nontrivial, well...