Remove @babel/plugin-transform-classes

[oliviertassinari]

To Reproduce

next.js/packages/next/src/build/babel/preset.ts

Lines 159 to 162 in 5ff2731

	[
	require('next/dist/compiled/babel/plugin-proposal-class-properties'),
	options['class-properties'] || {},
	],

Current vs. Expected behavior

Include @babel/plugin-transform-classes vs. Removed

Provide environment information

HEAD

Which area(s) are affected? (Select all that apply)

Performance, Runtime

Which stage(s) are affected? (Select all that apply)

next dev (local), next build (local), next start (local), Vercel (Deployed), Other (Deployed)

Additional context

I saw it in https://pagespeed.web.dev/analysis?url=https%3A%2F%2Fdeploy-preview-42140--material-ui.netlify.app%2F

Lighthouse warns about the use of legacy transformations, from https://github.com/GoogleChrome/lighthouse/blob/369979f498bd6560127e10476edffb264d4fa3b9/core/audits/byte-efficiency/legacy-javascript.js#L301.

By the look of today's browser support for ES6 Class https://caniuse.com/es6-class, it seems like we should be able to remove this from the default Babel plugin configuration and leave it to be added opt-in by developers. At least, if not for the next major release, in the next few months.