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/simple/client/openpitrix/helmrepoindex/repo_index.go

@@ -24,7 +24,6 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"strings"
 	"time"
 
@@ -275,7 +274,7 @@ func ByteArrayToSavedIndex(data []byte) (*SavedIndex, error) {
 		return nil, err
 	}
 	r.Close()
-	b, err := ioutil.ReadAll(r)
+	b, err := io.ReadAll(r)
 
 	if err != nil && err != io.EOF {
 		return nil, err