Adding missing return type to pi_estimator function (#13427)

- Add -> None return type annotation to pi_estimator function
- Improves code clarity and follows Python type hinting best practices
- Function already had proper type hints for parameters

Co-authored-by: Gunish Mukherji <gunishmukherji@Gunishs-MacBook-Air.local>
Co-authored-by: Maxim Smolskiy <mithridatus@mail.ru>

Author: 3 people

maths/monte_carlo.py

@@ -8,7 +8,7 @@
 from statistics import mean
 
 
-def pi_estimator(iterations: int):
+def pi_estimator(iterations: int) -> None:
     """
     An implementation of the Monte Carlo method used to find pi.
     1. Draw a 2x2 square centred at (0,0).