admin check index failed due to tidb_mem_quota_query limit

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
1、add index for table
2、admin check index
tableSize : 10000000

### 2. What did you expect to see? (Required)
admin check index success

### 3. What did you see instead (Required)
admin check index failed with below error

Error 1105 (HY000): Your query has been cancelled due to exceeding the allowed memory limit for a single SQL query. Please try narrowing your query scope or increase the tidb_mem_quota_query limit and try again.[conn=0]

### 4. What is your TiDB version? (Required)
./tidb-server -V
Release Version: v7.4.0-alpha
Edition: Community
Git Commit Hash: 0f41cfe2a8e71447f8c381f1b3380b82437f0b34
Git Branch: heads/refs/tags/v7.4.0-alpha
UTC Build Time: 2023-08-10 13:54:56
GoVersion: go1.21.0
Race Enabled: false
Check Table Before Drop: false
Store: unistore