Remove "tut" from the "build-systems" pipeline

PR #32615 deprecated Python versions up to 3.6.X. Since
the "build-systems" pipeline requires Python 3.6.15 to
build "tut", it will fail on the first rebuild that
involves Python.

The "tut" package is meant to perform an end-to-end
test of the "Waf" build-system, which is scarcely
used. The fix therefore is just to remove it from
the pipeline.

share/spack/gitlab/cloud_pipelines/stacks/build_systems/spack.yaml

@@ -16,7 +16,6 @@ spack:
     - default_specs:
       - lz4  # MakefilePackage
       - mpich~fortran  # AutotoolsPackage
-      - tut  # WafPackage
       - py-setuptools  # PythonPackage
       - openjpeg  # CMakePackage
       - r-rcpp  # RPackage