[webrtc-pc] Pull Request: Hide test annotations by default

dontcallmedom has just submitted a new pull request for https://github.com/w3c/webrtc-pc:

== Hide test annotations by default ==
They remain available through the command in the ReSpec Menu 'toggle test annotations'
close #2161

See https://github.com/w3c/webrtc-pc/pull/2262