Revert "TST: skip python-dateutil version sensitive tests until #12944 can resolve"

This reverts commit 1617244.

Author: jreback

pandas/tseries/tests/test_tslib.py

@@ -592,8 +592,6 @@ def test_parsers_quarter_invalid(self):
             self.assertRaises(ValueError, tools.parse_time_string, case)
 
     def test_parsers_dayfirst_yearfirst(self):
-        raise nose.SkipTest("skipping until comprehensive fixes for dateutil, "
-                            "xref #12944")
 
         # https://github.com/dateutil/dateutil/issues/217
         # this issue was closed