contrib: mingw64: update d3d12

Qt 6.7 requires[1] ID3D12Device2_INTERFACE_DEFINED for d3d12 abstraction which comes with MinGW64 v12.

[1] qrhid3d12_p.h @ L32:
// ID3D12Device2 and ID3D12GraphicsCommandList1 and types and enums introduced
// with those are hard requirements now. These should be declared in any
// moderately recent d3d12.h, but if it is an SDK from before Windows 10
// version 1703 then these types could be missing. In the absence of other
// options, handle this by skipping all the code and making QRhi::create() fail
// in such builds.

Request review @robUx4.