Do not use ClassVars with generic variables (#6348)

stdlib/ctypes/__init__.pyi

@@ -173,7 +173,7 @@ def POINTER(type: Type[_CT]) -> Type[pointer[_CT]]: ...
 # ctypes._Pointer in that it is the base class for all pointer types. Unlike the real _Pointer,
 # it can be instantiated directly (to mimic the behavior of the real pointer function).
 class pointer(Generic[_CT], _PointerLike, _CData):
-    _type_: ClassVar[Type[_CT]]
+    _type_: Type[_CT]
     contents: _CT
     def __init__(self, arg: _CT = ...) -> None: ...
     @overload
@@ -268,8 +268,8 @@ class BigEndianStructure(Structure): ...
 class LittleEndianStructure(Structure): ...
 
 class Array(Generic[_CT], _CData):
-    _length_: ClassVar[int]
-    _type_: ClassVar[Type[_CT]]
+    _length_: int
+    _type_: Type[_CT]
     raw: bytes  # Note: only available if _CT == c_char
     value: Any  # Note: bytes if _CT == c_char, str if _CT == c_wchar, unavailable otherwise
     # TODO These methods cannot be annotated correctly at the moment.