Can't drop placement policy if policyName is part of the policyName used by range

[jiyfhust]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create placement policy mypolicy followers=4;
create placement policy mypolicy2 followers=2;
alter range global placement policy mypolicy2;
drop placement policy mypolicy;

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

drop mypolicy return success.

3. What did you see instead (Required)

mysql> create placement policy mypolicy followers=4;
Query OK, 0 rows affected (0.11 sec)

mysql> create placement policy mypolicy2 followers=2;
Query OK, 0 rows affected (0.11 sec)

mysql> alter range global placement policy mypolicy2;
Query OK, 0 rows affected (0.00 sec)

mysql> drop placement policy mypolicy;
ERROR 8241 (HY000): Placement policy 'mypolicy' is still in use

4. What is your TiDB version? (Required)

master

[kennedy8312]

alter range global placement policy mypolicy2; seems to be supported starting from v7.5.0.

[jiyfhust]

/label affects-7.5