Fix pyfaust.circ bug occurring if len(v) == 4.

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ERROR: test_circulant (__main__.TestFaustPyCplx.test_circulant)
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Traceback (most recent call last):
  File /home/gitlab-runner/builds/miE7iDyU/0/faustgrp/faust/misc/test/src/Python//test_FaustPy.py, line 908, in test_circulant
    self.assertTrue(np.allclose(circulant(v), circ(v).toarray()))
                                              ^^^^^^^
  File /home/gitlab-runner/builds/miE7iDyU/0/faustgrp/faust/build_FaustLinuxPython/wrapper/python/pyfaust/__init__.py, line 4030, in circ
    left = left @ Faust(FwP.factors(nfwp-1) @ S)
           ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  File /home/gitlab-runner/.local/lib/python3.11/site-packages/scipy/sparse/_base.py, line 630, in __matmul__
    return self._mul_dispatch(other)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File /home/gitlab-runner/.local/lib/python3.11/site-packages/scipy/sparse/_base.py, line 544, in _mul_dispatch
    other_a = np.asanyarray(other)
              ^^^^^^^^^^^^^^^^^^^^
ValueError: object __array__ method not producing an array

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