Why does an error occur when I restore placement rules to a cluster?

Before v6.0.0, BR does not support placement rules. Starting from v6.0.0, BR supports placement rules and introduces a command-line option --with-tidb-placement-mode=strict/ignore to control the backup and restore mode of placement rules. With the default value strict, BR imports and validates placement rules, but ignores all placement rules when the value is ignore.