test overlaps without ghosts for charge density and bulk velocity

[UCaromel]

With #1083 we no longer test for charge density and bulk velocity in the test overlap:

PHARE/tests/simulator/test_advance.py

Line 408 in 7c18417

def _test_overlaped_fields_are_equal(self, datahier, time_step_nbr, time_step):

.
This is because this test check on ghost boxes, and we no longer maintain ghosts for these 2 quantities. However this test might still be interesting for shared border ?