test[next]: Use pytest marker to skip GTIR test (fix spack build)

[edopao]

The import dace statement causes the Spack build (spack-c2sm) to fail:

ImportError while importing test module '/scratch/snx3000/epaone/repo/gt4py/tests/next_tests/integration_tests/feature_tests/iterator_tests/test_program.py'.

    import dace
E   ModuleNotFoundError: No module named 'dace'

Use the pytest marker to avoid this error.

[edopao]

cscs-ci run default