kes: remove unnecessary error conversion (#14459)

This commit removes some duplicate code that
converts KES API errors.

This code was added since KES `0.18.0` changed
some exported API errors. However, the KES SDK
handles this error conversion itself.
Therefore, it is not necessary to duplicate this
behavior in MinIO.

See: 21555fa624/error.go (L94)

Signed-off-by: Andreas Auernhammer <hi@aead.dev>

cmd/admin-handler-utils.go

@@ -22,8 +22,7 @@ import (
 	"errors"
 	"net/http"
 
-	"github.com/minio/minio/internal/kms"
-
+	"github.com/minio/kes"
 	"github.com/minio/madmin-go"
 	"github.com/minio/minio/internal/auth"
 	"github.com/minio/minio/internal/config"
@@ -145,7 +144,7 @@ func toAdminAPIErr(ctx context.Context, err error) APIError {
 				Description:    "The policy cannot be removed, as it is in use",
 				HTTPStatusCode: http.StatusBadRequest,
 			}
-		case kms.KeyExists(err):
+		case errors.Is(err, kes.ErrKeyExists):
 			apiErr = APIError{
 				Code:           "XMinioKMSKeyExists",
 				Description:    err.Error(),