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/svg/discover_nobindata.go

@@ -8,7 +8,7 @@
 package svg
 
 import (
-	"io/ioutil"
+	"os"
 	"path/filepath"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -20,7 +20,7 @@ func Discover() map[string]string {
 
 	files, _ := filepath.Glob(filepath.Join(setting.StaticRootPath, "public", "img", "svg", "*.svg"))
 	for _, file := range files {
-		content, err := ioutil.ReadFile(file)
+		content, err := os.ReadFile(file)
 		if err == nil {
 			filename := filepath.Base(file)
 			svgs[filename[:len(filename)-4]] = string(content)