calls `treq.Response.collect` without logcontext wrapping

[Richard van der Hoff]

check_event_for_spam calls await response.collect(...).

treq.Response.collect is non-synapse code which returns a Deferred; accordingly you need to call make_deferred_yieldable on the Deferred before it is safe to await from inside synapse code (otherwise you will leak logcontexts).

[David Teller]

The entire method has been rewritten and await response.collect(...) has disappeared at some point.