🚀 Feature: Remove the long-deprecated --compilers option

[JoshuaKGoldberg]

Feature Request Checklist

• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I want to provide a PR to resolve this

Overview

As of #3038, --compilers is deprecated and non-functional. I've yet to see anybody use it in any real projects. But the code still exists:

mocha/lib/cli/run.js

Lines 334 to 339 in e3da641

	if (argv.compilers) {
	throw createUnsupportedError(
	`--compilers is DEPRECATED and no longer supported.
	See https://github.com/mochajs/mocha/wiki/compilers-deprecation for migration information.`
	);
	}

This is dead weight on the project. IMO there's no real need to keep it around given how it's been deprecated with a loud warning & migration docs (https://github.com/mochajs/mocha/wiki/compilers-deprecation) for 7 years.

Suggested Solution

I propose we remove it in a future major version, such as Mocha 12.

Alternatives

We could leave it in, but all it does now is throw createUnsupportedError.

Additional Info

Similar sibling issue: #5243

[JoshuaKGoldberg]

Marking as accepting PRs. Note that we won't be able to merge it until we start merging PRs for Mocha v12. Which will be an unknown, not-very-soon time from now.