Remove usage of PushSource? #304
Description
Companion ticket for ssbc/go-luigi#5.
Seems like it's not used much?
grep -iR "PushSource" .
./cmd/ssb-truncate-log/truncate.go: err = src.(luigi.PushSource).Push(context.TODO(), luigi.FuncSink(func(ctx context.Context, v interface{}, err error) error {
./cmd/ssb-logcat/main.go: err = src.(luigi.PushSource).Push(context.TODO(), luigi.FuncSink(func(ctx context.Context, v interface{}, err error) error {