Remove isMaster usage once drop support for Node.js version 14

[ananzh]

Description

In our codebase, we have a TODO note indicating that we're using the cluster.isMaster property for Node.js 14 support and the cluster.isPrimary property for Node.js 18+.

Here's the specific line of code:

// ToDo: `isMaster` is a Node 14- prop; remove it when Node 18+ is the only engine supported
const isClusterManager = cluster.isPrimary ?? cluster.isMaster;

This issue tracks the removal of cluster.isMaster once we drop support for Node.js version 14.