refactor: move from io/ioutil to io and os packages (#5266)

The io/ioutil package has been deprecated as of Go 1.16 [1]. This commit
replaces the existing io/ioutil functions with their new definitions in
io and os packages.

[1]: https://golang.org/doc/go1.16#ioutil
Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

pkg/test/testing.go

@@ -20,7 +20,7 @@ import (
 	"context"
 	"fmt"
 	"io"
-	"io/ioutil"
+	"os"
 	"strconv"
 	"strings"
 	"testing"
@@ -107,7 +107,7 @@ func (t *TestCtx) Setup(yamlPath string, crdPath string, schemes ...AddToSchemeF
 	if err != nil {
 		return err
 	}
-	bytes, err := ioutil.ReadFile(yamlPath)
+	bytes, err := os.ReadFile(yamlPath)
 	if err != nil {
 		klog.Errorln("Failed to read yaml file")
 		return err