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/generic-handlers.go

@@ -33,8 +33,6 @@ import (
 	"github.com/minio/minio-go/v7/pkg/set"
 	"github.com/minio/minio/internal/grid"
 	xnet "github.com/minio/pkg/v3/net"
-	"golang.org/x/exp/maps"
-	"golang.org/x/exp/slices"
 
 	"github.com/minio/minio/internal/amztime"
 	"github.com/minio/minio/internal/config/dns"
@@ -75,7 +73,7 @@ const (
 // and must not set by clients
 func containsReservedMetadata(header http.Header) bool {
 	for key := range header {
-		if slices.Contains(maps.Keys(validSSEReplicationHeaders), key) {
+		if _, ok := validSSEReplicationHeaders[key]; ok {
 			return false
 		}
 		if stringsHasPrefixFold(key, ReservedMetadataPrefix) {