cherry pick #3208 to release-4.0 (#3228)

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

Co-authored-by: Null not nil <67764674+nullnotnil@users.noreply.github.com>

TOC.md

@@ -271,6 +271,7 @@
       + [`REVOKE <role>`](/sql-statements/sql-statement-revoke-role.md)
       + [`ROLLBACK`](/sql-statements/sql-statement-rollback.md)
       + [`SELECT`](/sql-statements/sql-statement-select.md)
+      + [`SET DEFAULT ROLE`](/sql-statements/sql-statement-set-default-role.md)
       + [`SET [NAMES|CHARACTER SET]`](/sql-statements/sql-statement-set-names.md)
       + [`SET PASSWORD`](/sql-statements/sql-statement-set-password.md)
       + [`SET ROLE`](/sql-statements/sql-statement-set-role.md)
@@ -289,7 +290,6 @@
       + [`SHOW CREATE USER`](/sql-statements/sql-statement-show-create-user.md)
       + [`SHOW DATABASES`](/sql-statements/sql-statement-show-databases.md)
       + [`SHOW DRAINER STATUS`](/sql-statements/sql-statement-show-drainer-status.md)
-      + [`SHOW DEFAULT ROLE`](/sql-statements/sql-statement-set-default-role.md)
       + [`SHOW ENGINES`](/sql-statements/sql-statement-show-engines.md)
       + [`SHOW ERRORS`](/sql-statements/sql-statement-show-errors.md)
       + [`SHOW [FULL] FIELDS FROM`](/sql-statements/sql-statement-show-fields-from.md)