Inheritance w/ Schema: ClassVar[Type[Schema]] is broken as of 8.5.6

[ghost]

PR #189 introduced a regression where inheritance between dataclasses w/ explicit ClassVar[Type[Schema]]'s in parents is broken. The WAR from the PR was to drop it off of parents, but it'd be nice to see it fixed for those of us that love type-checking and hinting.

From that PR's comment chain:

@dataclass
class ThingA:
    Schema: ClassVar[Type[Schema]]
    name: str

@dataclass
class ThingB(ThingA):
    Schema: ClassVar[Type[Schema]]
    short_name: str