refactor: replace experimental maps and slices with stdlib (#20679)

The experimental functions are now available in the standard library in
Go 1.23 [1].

[1]: https://go.dev/doc/go1.23#new-unique-package

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

cmd/peer-s3-client.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"slices"
 	"sort"
 	"strconv"
 	"sync/atomic"
@@ -29,7 +30,6 @@ import (
 	"github.com/minio/madmin-go/v3"
 	"github.com/minio/minio/internal/grid"
 	"github.com/minio/pkg/v3/sync/errgroup"
-	"golang.org/x/exp/slices"
 )
 
 var errPeerOffline = errors.New("peer is offline")