Remove PhantomJS stuff

[jimmywarting]

I saw this and though, nobody is using phantomjs. it's a headless browser that no real user is using. it was based on webkit and the development have been discontinued. think you should remove this kind of things and instead use something like puppeteer or something.

https://github.com/less/less.js/blob/eefe33a47f6fdcc228817df7435a1770ce9e51ea/packages/less/src/less-browser/index.js#L49-L56

PhantomJS is depricated and should not be used anymore.

[matthew-dean]

Current tests use mocha-headless-chrome which uses Puppeteer, so @jimmywarting feel free to make a PR.

[gadzbi123]

This issue can be closed in reference to #3792

[IAmRiteshKoushik]

Is this issue still up-for-grabs or has it been resolved ? If someone could help me out here a bit, then I would like to take up the issue and try resolving it.

[TusharP05]

is someone working on this? I will be happy to take up this issue and contribute.

[Groot-2001]

Hey @matthew-dean , I would like to work on this issue!