Optimize authenticator oidc test

Signed-off-by: iutx <root@viper.run>

Kubernetes-commit: c21d33ab280f68176911e064ccff41ac2b96bbe3

plugin/pkg/authenticator/token/oidc/oidc_test.go

@@ -25,9 +25,9 @@ import (
 	"encoding/json"
 	"encoding/pem"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"reflect"
 	"strings"
 	"testing"
@@ -76,7 +76,7 @@ func loadECDSAPrivKey(t *testing.T, filepath string, alg jose.SignatureAlgorithm
 }
 
 func loadKey(t *testing.T, filepath string, alg jose.SignatureAlgorithm, unmarshal func([]byte) (interface{}, error)) *jose.JSONWebKey {
-	data, err := ioutil.ReadFile(filepath)
+	data, err := os.ReadFile(filepath)
 	if err != nil {
 		t.Fatalf("load file: %v", err)
 	}