Fix the doctest due to numpy 2.0 (pytorch#654)

Summary:
Pull Request resolved: pytorch#654

Doctest fails due to numpy's upgrade into 2.0, which changes the way of printing.
astropy/astropy#15095

Differential Revision: D58873298

opacus/accountants/analysis/rdp.py

@@ -39,7 +39,7 @@
     ...     rdp += compute_rdp(q=q, noise_multiplier=sigma, steps=steps, orders=orders)
 
     >>> epsilon, opt_order = get_privacy_spent(orders=orders, rdp=rdp, delta=1e-5)
-    >>> epsilon, opt_order  # doctest: +NUMBER
+    >>> float(epsilon), int(opt_order)  # doctest: +NUMBER
     (0.336, 23)
 
 """