Now that all casper tests have been migrated to
puppeteer, there's no need for having casper
related things.
Removed the casperjs package and removed/replaced
casper in few places with puppeteer.
Only removed few of them which I'm confident
about. Also didn't make any changes in docs
as it would be easier to remove them while
adding puppeteer docs.
ES and TypeScript modules are strict by default and don’t need this
directive. ESLint will remind us to add it to new CommonJS files and
remove it from ES and TypeScript modules.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
