multi: fix newly detected linter issues

contractcourt/htlc_timeout_resolver_test.go

@@ -1218,7 +1218,7 @@ func TestHtlcTimeoutSecondStageSweeperRemoteSpend(t *testing.T) {
 				// expect the resolver to re-subscribe to a
 				// spend, hence we must resend it.
 				if resumed {
-					fmt.Println("resumed")
+					t.Logf("resumed")
 					ctx.notifier.SpendChan <- &chainntnfs.SpendDetail{
 						SpendingTx:    spendTx,
 						SpenderTxHash: &spendTxHash,