Update nf-processenv-setstdhandleex.md

[RatinCN]

• SetStdHandleEx is a NT6 API, see also "processenv.h" in Windows SDK:

#if (_WIN32_WINNT >= 0x0600)

WINBASEAPI
BOOL
WINAPI
SetStdHandleEx(
    _In_ DWORD nStdHandle,
    _In_ HANDLE hHandle,
    _Out_opt_ PHANDLE phPrevValue
    );

#endif // _WIN32_WINNT >= 0x0600

• It returns BOOL, zero means failed and nonzero means succeeded. S_OK is 0, which should be a HRESULT value.

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