the scope in error message is wrong

[morgo]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

select @@session.max_connections;
select @@global.last_insert_id;

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

tidb> select @@session.max_connections;
ERROR 1238 (HY000): Variable 'max_connections' is a GLOBAL variable
tidb> select @@global.last_insert_id;
ERROR 1238 (HY000): Variable 'last_insert_id' is a SESSION variable

3. What did you see instead (Required)

tidb> select @@session.max_connections;
ERROR 1238 (HY000): Variable 'max_connections' is a SESSION variable
tidb> select @@global.last_insert_id;
ERROR 1238 (HY000): Variable 'last_insert_id' is a GLOBAL variable

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.