Correct version of dependency used in example

[daniel-augusto]

In https://docs.web3j.io/4.8.7/quickstart/#maven-plugin, do references to version 4.8.1 of web3j-maven-plugin but this version does not exist in mvnrepository (https://mvnrepository.com/artifact/org.web3j/web3j-maven-plugin) neither releases page of own project: https://github.com/web3j/web3j-maven-plugin/releases.

The correct version is 4.8.2, present in mvnrepository and release page.