win32: do not use __declspec(restrict) with the Windows SDK

restrict is forcibly defined to __restrict for C++ compatibility, even with cl.exe (but also with clang-cl). And __declspec(__restrict) is not valid, it creates a lot of warnings.

__declspec(__restrict) is only used in corecrt_malloc.h in MSVC and the Windows SDK. See https://learn.microsoft.com/en-us/cpp/cpp/restrict?view=msvc-170

This prevents a bit of optimization for allocated memory usage.