Fix qgrid/tests/test_grid.py::test_edit_date

Before this change the test fails with the message:

    FAILED qgrid/tests/test_grid.py::test_edit_date - AssertionError: assert '2013-01-02T00:00:00.000' == '2013-01-02T00:00:00.000Z'

After this change the test passes.

Author: maxwell-k

qgrid/tests/test_grid.py

@@ -66,9 +66,9 @@ def test_edit_date():
         "Date",
         3,
         pd.Timestamp("2013-01-02 00:00:00"),
-        "2013-01-02T00:00:00.000Z",
+        "2013-01-02T00:00:00.000",
         pd.Timestamp("2013-01-16 00:00:00"),
-        "2013-01-16T00:00:00.000Z",
+        "2013-01-16T00:00:00.000",
     )