TST: flaky TestSOSFreqz::test_fs_param

* deals with the 1 of the 2 Apple silicon
test failures in gh-18732

* I was able to reproduce locally, but because
it was flaky I needed `pytest-repeat` for
consistent failure:
`CC=clang CXX=clang++ FC=gfortran-12 python dev.py test -t scipy/signal/tests/test_filter_design.py::TestSOSFreqz::test_fs_param -- --count=200`

* I verified that with the provided patch/`atol` bump,
we consistently pass even with `2000` repeats

[skip circle]

scipy/signal/tests/test_filter_design.py

@@ -1041,7 +1041,7 @@ def test_fs_param(self):
         # N = None, whole=True
         w1, h1 = sosfreqz(sos, whole=True, fs=fs)
         w2, h2 = sosfreqz(sos, whole=True)
-        assert_allclose(h1, h2)
+        assert_allclose(h1, h2, atol=1e-27)
         assert_allclose(w1, np.linspace(0, fs, 512, endpoint=False))
 
         # N = 5, whole=False