Drop support for webpack-cli ^4.9.1

[Kocal]

Currently we support ^4.9.1 || ^5.0.1, but for the next Encore major release, I suppose we can drop the support of ^4.9.1 version (will remove Webpack 4 compatibility)

https://github.com/webpack/webpack-cli/blob/master/CHANGELOG.md#500-2022-11-17