go/ssa/interp: remove unused import

Updates golang/go#34089

Change-Id: Ic7cc45803a31394241c7fa33092ec566dbf296ca
Reviewed-on: https://go-review.googlesource.com/c/tools/+/220959
Run-TryBot: Jay Conrod <[email protected]>
Reviewed-by: Michael Matloob <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>

Author: Jay Conrod

go/ssa/interp/interp_test.go

@@ -23,7 +23,6 @@ import (
 	"log"
 	"os"
 	"path/filepath"
-	"runtime"
 	"strings"
 	"testing"
 	"time"