revert cast

Signed-off-by: Jonathan Schwender <jonathan.schwender@huawei.com>

Author: jschwe

src/platform/windows/wgl/context.rs

@@ -659,7 +659,7 @@ fn extension_loader_thread() -> WGLExtensionFunctions {
         let mut extension_functions = WGLExtensionFunctions::default();
         let window = winuser::CreateWindowExA(
             0,
-            window_class_atom.cast(),
+            window_class_atom as LPCSTR,
             window_class_name,
             WS_OVERLAPPEDWINDOW | WS_VISIBLE,
             0,