grpc: Replace WithInsecure

grpc.WithInsecure has been deprecated, replaced with the suggested
alterative.

js/modules/k6/grpc/client.go

@@ -38,6 +38,7 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/credentials/insecure"
 	"google.golang.org/grpc/metadata"
 	grpcstats "google.golang.org/grpc/stats"
 	"google.golang.org/grpc/status"
@@ -151,7 +152,7 @@ func (c *Client) Connect(addr string, params map[string]interface{}) (bool, erro
 
 		opts = append(opts, grpc.WithTransportCredentials(credentials.NewTLS(tlsCfg)))
 	} else {
-		opts = append(opts, grpc.WithInsecure())
+		opts = append(opts, grpc.WithTransportCredentials(insecure.NewCredentials()))
 	}
 
 	if ua := state.Options.UserAgent; ua.Valid {