Replace usage of np.float with float (#147) (#150)

The epr_numerical_diagonalization function uses np.float which has been
deprecated in Numpy.

Refer https://numpy.org/devdocs/release/1.20.0-notes.html#deprecations

The continued usage of np.float yields the following error in the
epr_numerical_diaganolization function when later versions of Numpy is used.

"AttributeError: module 'numpy' has no attribute 'float'."

This commit replace np.float with float to solve this error.

pyEPR/calcs/back_box_numeric.py

@@ -63,7 +63,7 @@ def epr_numerical_diagonalization(freqs, Ljs, ϕzpf,
     assert(all(Ljs < 1E-3)
            ), "Please input the inductances in Henries. \N{nauseated face}"
 
-    Hs = black_box_hamiltonian(freqs * 1E9, Ljs.astype(np.float), fluxQ*ϕzpf,
+    Hs = black_box_hamiltonian(freqs * 1E9, Ljs.astype(float), fluxQ*ϕzpf,
                                cos_trunc, fock_trunc, individual=use_1st_order,
                                non_linear_potential = non_linear_potential)
     f_ND, χ_ND, _, _ = make_dispersive(