itertools.tee->instance->attribute->itertools.tee and
itertools.tee->teedataobject->itertools.tee cycles, which can be found now
that itertools.tee and its teedataobject participate in GC, remain findable
and cleanable. The test won't fail when they aren't, but at least the
frequent hunt-refleaks runs would spot the rise in refleaks.