[whatwg/fetch] Draft changes to "obtain a websocket connection" (#1244)

Modify "obtain a websocket connection" section to explicitly describe
throttling behaviour rather than delegating it to RFC6455.

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You can view, comment on, or merge this pull request online at:

  https://github.com/whatwg/fetch/pull/1244


-- Commit Summary --

  * Draft changes to "obtain a websocket connection"

-- File Changes --

    M fetch.bs (57)

-- Patch Links --

https://github.com/whatwg/fetch/pull/1244.patch

https://github.com/whatwg/fetch/pull/1244.diff


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