refactor: move from io/ioutil to io and os package (#17109)

The io/ioutil package has been deprecated as of Go 1.16, see
https://golang.org/doc/go1.16#ioutil. This commit replaces the existing
io/ioutil functions with their new definitions in io and os packages.

Signed-off-by: Eng Zer Jun <engzerjun@gmail.com>

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

modules/git/repo_index.go

@@ -7,7 +7,6 @@ package git
 import (
 	"bytes"
 	"context"
-	"io/ioutil"
 	"os"
 	"strings"
 
@@ -47,7 +46,7 @@ func (repo *Repository) readTreeToIndex(id SHA1, indexFilename ...string) error
 
 // ReadTreeToTemporaryIndex reads a treeish to a temporary index file
 func (repo *Repository) ReadTreeToTemporaryIndex(treeish string) (filename string, cancel context.CancelFunc, err error) {
-	tmpIndex, err := ioutil.TempFile("", "index")
+	tmpIndex, err := os.CreateTemp("", "index")
 	if err != nil {
 		return
 	}