Run modernize (#21546)

`go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...` executed.

`go generate ./...` ran afterwards to keep generated.

cmd/post-policy-fan-out.go

@@ -20,6 +20,7 @@ package cmd
 import (
 	"bytes"
 	"context"
+	"maps"
 	"sync"
 
 	"github.com/minio/minio-go/v7"
@@ -78,9 +79,7 @@ func fanOutPutObject(ctx context.Context, bucket string, objectAPI ObjectLayer,
 			}()
 
 			userDefined := make(map[string]string, len(req.UserMetadata))
-			for k, v := range req.UserMetadata {
-				userDefined[k] = v
-			}
+			maps.Copy(userDefined, req.UserMetadata)
 
 			tgs, err := tags.NewTags(req.UserTags, true)
 			if err != nil {