ddl: drop table should clean the placement bundle rules

[AilinKid]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

tiup playground v5.0.1 --tiflash 0  --kv 2 --db 1
create table t(a int) constraints="[-region=hdd]"
http://127.0.0.1:2379/pd/api/v1/config/placement-rule  // here you will find the placement rule for the new table t
set the appropriate gc_life_time and gc_life_interval
drop table t
select * from mysql.gc_delete_range                    // make sure the dropped table has been GCed.
http://127.0.0.1:2379/pd/api/v1/config/placement-rule  // here you will still find the placement rule for the new table t

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

After the gc is done, there will be no placement rules for the table t

3. What did you see instead (Required)

After the gc is done, placement rules for the table t still exists.

4. What is your TiDB version? (Required)

master

[github-actions]

Please check whether the issue should be labeled with 'affects-x.y' or 'fixes-x.y.z', and then remove 'needs-more-info' label.