Fix broken unit test cases due to rho formula change

tests/files/HH_G_FKSH14.txt

@@ -1,9 +1,9 @@
-0.00052396	0.000226929	0.000440667	0.000110308	0.000101161
+5.23960135e-04	1.86499079e-03	1.01160864e-04	1.04122326e-04	1.10307874e-04
 100	100	100	100	100
-0.000309816	0.00044554	0.000602407	0.000825617	0.000926138
+3.09816027e-04	4.47737604e-04	6.14144703e-04	8.43769672e-04	9.46402838e-04
 1	1	1	1	1
 0.919	0.919	0.919	0.919	0.919
-2.376e+07	6.70488e+07	1.39674e+08	2.2376e+09	3.10298e+09
-0.219786	0.206411	0.26511	1	1
-27135.1	65213.2	147459	785749	1.08605e+06
-0.901558	0.843668	0.865377	0.981156	0.981156
+2.37600000e+07	7.06355469e+07	1.54303879e+08	2.43121793e+09	3.37702221e+09
+2.19786132e-01	1.99041870e-01	2.49332391e-01	1	1
+2.71351174e+04	6.56456237e+04	1.49957507e+05	8.32908454e+05	1.15089302e+06
+9.01557789e-01	9.01557789e-01	8.58140704e-01	9.81155779e-01	9.77537688e-01

tests/test_helper_hh_calibration.py

@@ -15,8 +15,8 @@ def test_calc_rho(self):
         h = np.array([2, 3, 4, 5])
         Vs = np.array([200, 300, 400, 500])
         rho = hhc._calc_rho(h, Vs)
-        rho_ = np.array([1.6500, 2.0375, 1.9892, 1.9995]) * 1000
-        self.assertTrue(np.allclose(rho, rho_, rtol=0.001, atol=0.0))
+        expected_rho = np.array([1.6500, 2.1272, 2.1399, 2.1702]) * 1000
+        self.assertTrue(np.allclose(rho, expected_rho, rtol=0.001, atol=0.0))
 
     def test_calc_Gmax(self):
         rho = np.array([1600, 1700, 1800])