CI: skip testing on x86
CI: skip testing on x86

couldn't figure out why `import vapoursynth` fails with
ImportError: DLL load failed while importing vapoursynth: A dynamic link library (DLL) initialization routine failed.

It's better to skip testing on x86 than leaving CI failing for Windows.

Signed-off-by: akarin <042dc4512fa3d391c5170cf3aa61e6a638f84342@akarin.info>

vapoursynth/vapoursynth,vapoursynth/vapoursynth,vapoursynth/vapoursynth,vapoursynth/vapoursynth