Remove hybi sub directory for WebSocket layout tests

It was for differentiating two different versions of WebSocket when
Blink (WebKit) was supporting both. It's no longer necessary.

BUG=none

Review URL: https://codereview.chromium.org/101143002

git-svn-id: svn://svn.chromium.org/blink/trunk@163168 bbb929c8-8fbe-4397-9dbb-9b2b20218538