MDEV-29137 mariabackup excessive logging of ddl tracking

- Remove the FILE_MODIFY message from mariabackup which was
displaying the list of file names which were modified since
the previous checkpoint.

extra/mariabackup/xtrabackup.cc

@@ -896,7 +896,6 @@ static void backup_file_op_fail(ulint space_id, int type,
 				filename_to_spacename(name, len).c_str());
 		break;
 	case FILE_MODIFY:
-		msg("DDL tracking : modify %zu \"%.*s\"", space_id, int(len), name);
 		break;
 	case FILE_RENAME:
 		msg("DDL tracking : rename %zu \"%.*s\",\"%.*s\"",