Fix issues in typeshed builtins

[ndmitchell]

When checking typeshed there are three errors (if you ignore the overrides):

ERROR bundled /pyrefly/third_party/typeshed/enum.pyi:230:9-14: The value for enum member `value` must match the annotation of the _value_ attribute [bad-assignment]
ERROR bundled /pyrefly/third_party/typeshed/enum.pyi:243:9-14: The value for enum member `value` must match the annotation of the _value_ attribute [bad-assignment]
ERROR bundled /pyrefly/third_party/typeshed/importlib/metadata/__init__.pyi:63:5-12: `ClassVar` may not be used for TypedDict or NamedTuple members [invalid-annotation]

For now I'm going to suppress them in the implicit config file, but we should really fix them.