Fix miscellaneous invalid TypeVar usages (#8074)

stdlib/ctypes/__init__.pyi

@@ -164,7 +164,7 @@ def POINTER(type: type[_CT]) -> type[pointer[_CT]]: ...
 class pointer(Generic[_CT], _PointerLike, _CData):
     _type_: type[_CT]
     contents: _CT
-    def __init__(self, arg: _CT = ...) -> None: ...
+    def __init__(self, arg: _CT) -> None: ...
     @overload
     def __getitem__(self, __i: int) -> _CT: ...
     @overload