Canvas sometimes does not respond with users, even when we ask

In order to get the groups for a user we ask for the whole course groups and ask Canvas to tack on some information about users. We then filter this information to the user to get their groups.

Sometimes Canvas decides not to send us this information. This shows up to the user as an error in Speedgrader and was noted in Sentry in:

* https://sentry.io/organizations/hypothesis/issues/3604779293/?project=259908&referrer=slack

A ticket was made, but only fixed the symptom here:

* https://github.com/hypothesis/lms/pull/4474

This causes us to not error, but the user is stuck with a spinner instead.