Used linear filtering when converting chroma in D3D.

It seems to also be used for chroma upsampling.
It fixes #5751.

modules/video_output/msw/direct3d.c

@@ -1166,7 +1166,7 @@ static int Direct3DImportPicture(vout_display_t *vd,
 
     /* Copy picture surface into texture surface
      * color space conversion happen here */
-    hr = IDirect3DDevice9_StretchRect(sys->d3ddev, source, NULL, destination, NULL, D3DTEXF_NONE);
+    hr = IDirect3DDevice9_StretchRect(sys->d3ddev, source, NULL, destination, NULL, D3DTEXF_LINEAR);
     IDirect3DSurface9_Release(destination);
     if (FAILED(hr)) {
         msg_Dbg(vd, "%s:%d (hr=0x%0lX)", __FUNCTION__, __LINE__, hr);