Peek's `Peek.request_id` method doesn't work well with a multi-threaded
server and concurrent requests, because requests can 'steal' another
request's ID, or unset it before it was due.

The upstream change resolves this; the commit here is just to ensure
that GitLab works with that upstream change, mostly by not using
`Peek.request_id` any more (as the method doesn't exist).