fix query fields on tidb_background_subtask to avoid error when upgrade

[D3Hunter]

Bug Report

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1. Minimal reproduce step (Required)

we might add new fields in the table, to avoid upgrade fail we need fix the selected fields

only affects 7.5, master has change it in #49020

tidb/pkg/disttask/framework/storage/task_table.go

Line 391 in 6b8d834

rs, err := stm.executeSQLWithNewSession(ctx, `select * from mysql.tidb_background_subtask

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

3. What did you see instead (Required)

4. What is your TiDB version? (Required)