Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

1. create a cluster with tidb config new_collations_enabled_on_first_bootstrap: false.
2. create a table with collation 'utf8mb4_0900_ai_ci': create table books (idbigint auto_increment,name varchar(64), primary key (id)) CHARSET utf8mb4 COLLATE utf8mb4_0900_ai_ci;
3. insert several records to the table.
4. execute a full backup
5. create another cluster tidb config new_collations_enabled_on_first_bootstrap: false.
6. restore the backup to the new cluster

2. What did you expect to see? (Required)

restore successfully

3. What did you see instead (Required)

restore failed with error Error: [ddl:1273]Unsupported collation when new collation is enabled: 'utf8mb4_0900_ai_ci'

4. What is your TiDB version? (Required)

v6.1.0