Removed unused mock_dem

@pytest.fixture

def mock_dem():

    mock_dem = mock.MagicMock(spec_set=GeoDataset)

    #mock_dem.read_array.return_value = 100

    #mock_dem.latlon_to_pixel.return_value = (0.5,0.5)

    mock_dem.read_array.return_value = 100

    mock_dem.latlon_to_pixel.return_value = (0.5,0.5)

    return mock_dem

@pytest.fixture