remove phantomjs

https://github.com/crypto-browserify/randombytes/blob/f18ded32b209f0d4c637608a11ae042ae96b4c2e/browser.js#L25-L26

Phantomjs is suspended and not being worked on any longer. 
Phantomjs have never been a browser that anyone is using due to lack of any UI. it was solo used for testing and scripting automation, so it's very unpopular
ppl start using headless chrome or firefox nowdays