use regular WTForms DateField for requests dates

tests/domain/test_date.py

@@ -1,20 +0,0 @@
-import pytest
-import pendulum
-
-from atst.domain.date import parse_date
-
-
-def test_date_with_slashes():
-    date_str = "1/2/2020"
-    assert parse_date(date_str) == pendulum.date(2020, 1, 2)
-
-
-def test_date_with_dashes():
-    date_str = "2020-1-2"
-    assert parse_date(date_str) == pendulum.date(2020, 1, 2)
-
-
-def test_invalid_date():
-    date_str = "This is not a valid data"
-    with pytest.raises(ValueError):
-        parse_date(date_str)