TST: xfail unrelaible parallel coordinates sorted label test (#18688)

Author: jreback

pandas/tests/plotting/test_misc.py

@@ -201,6 +201,7 @@ def test_parallel_coordinates(self):
         with tm.assert_produces_warning(FutureWarning):
             parallel_coordinates(df, 'Name', colors=colors)
 
+    @pytest.mark.xfail(reason="unreliable test")
     def test_parallel_coordinates_with_sorted_labels(self):
         """ For #15908 """
         from pandas.plotting import parallel_coordinates