The value of oom-action in tidb log is different from the real value

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)
1. setup tidb cluster of version < 4.0.11: `tiup cluster deploy gjt_test v4.0.9 ./ch_cluster.yaml`
2. upgrade tidb cluster ov version >= 4.0.11: `tiup cluster upgrade gjt_test v5.0.6`
3. conn tidb then check the real oom-action(`show config where name = 'oom-action'`): it should be `log`
4. check tidb.log, `grep 'print.go.*oom-action'`, you can see oom-action is `cancel`, which is different from the real value. It's confusing.

### 2. What did you expect to see? (Required)
The output of `show config where name = 'oom-action'` should be same the value in tidb.log

### 3. What did you see instead (Required)
They are differnet.
### 4. What is your TiDB version? (Required)
v4.0.9 and v5.0.6