Update Code Examples from Using Web3.js to Ethers.js

[codersjj]

Page

Introduction to Smart Contracts - A Simple Smart Contract - Subcurrency Example

Abstract

Web3.js libraries are being sunset on March 4th, 2025, as announced by the Web3.js team. Considering this, I propose updating the current Solidity documentation code examples to use Ethers.js instead of Web3.js.

Pull request

#15760

[cameel]

Sure, why not. If it's being deprecated, we should not be showing it in the intro.