Revert "chore(deps): update dependency ws to v6.1.1"

[abernix]

Reverts #1987

In diagnosing the problem exhibited on the CircleCI run for #2005, the problem bisected back to this commit which updated the ws types to a new patch version:

$ git bisect start master @{10.days.ago}
$ git bisect run sh -c 'npm run clean; npm i; npm i --no-save typescript@rc; npm t; sleep 5;'

The npm i --no-save typescript@rc is necessary to fix the now-broken nightly typescript@next version which had been in place at the time — which is what #2005 aimed to fix.

yielded:

bde56a6c76678292d7c6c32b849c07f8da9a6725 is the first bad commit
commit bde56a6c76678292d7c6c32b849c07f8da9a6725
Author: renovate[bot] <renovate[bot]@users.noreply.github.com>
Date:   Sat Nov 17 13:34:58 2018 +0000

    chore(deps): update dependency ws to v6.1.1 (#1987)

I haven't looked into it in more detail, but reverting this update does seem to resolve the problem. We'll likely have to revisit this soon, but this will hopefully unblock the barrage of PRs which are currently failing because of the TypeScript error demonstrated in #2005.