fileReservedTime配置被覆盖

### Before Creating the Bug Report

- [x] I found a bug, not just asking a question, which should be created in [GitHub Discussions](https://github.com/apache/rocketmq/discussions).

- [x] I have searched the [GitHub Issues](https://github.com/apache/rocketmq/issues) and [GitHub Discussions](https://github.com/apache/rocketmq/discussions) of this repository and believe that this is not a duplicate.

- [x] I have confirmed that this bug belongs to the current repository, not other repositories of RocketMQ.

### Runtime platform environment

linux

### RocketMQ version

5.3.2

### JDK Version

17.0.18

### Describe the Bug

查看broker状态后，配置fileReservedTime 会变成默认的72
命令：
```
sh bin/mqadmin getBrokerConfig \
-b localhost:10911 \
-n localhost:9876 | grep fileReservedTime
```
日志显示：
`AdminBrokerThread_9 - Replace, key: fileReservedTime, value: 168 -> 72`

### Steps to Reproduce

broker.conf
```
brokerClusterName = DefaultCluster
brokerName = broker-a
brokerId = 0
deleteWhen = 04
fileReservedTime = 168
#brokerRole = ASYNC_MASTER
#flushDiskType = ASYNC_FLUSH
brokerRole = SYNC_MASTER
flushDiskType = SYNC_FLUSH
```
start.sh
```
nohup sh bin/mqnamesrv &
sleep 3
nohup sh bin/mqbroker -n localhost:9876 -c conf/broker.conf -pc conf/proxy.json --enable-proxy &
```
执行查看命令：
```
sh bin/mqadmin getBrokerConfig \
-b localhost:10911 \
-n localhost:9876 | grep fileReservedTime
```
问题是：
查看broker状态后（或dashboard点cluster->config），配置fileReservedTime 会变成默认的72
命令：
```
sh bin/mqadmin getBrokerConfig \
-b localhost:10911 \
-n localhost:9876 | grep fileReservedTime
```
日志显示：
`AdminBrokerThread_9 - Replace, key: fileReservedTime, value: 168 -> 72`

### What Did You Expect to See?

期望按照broker.conf配置中的来，不要变

### What Did You See Instead?

无

### Additional Context

linux下 local模式部署

Reproduce the issue with conf/broker.conf and start.sh, then run mqadmin getBrokerConfig and inspect the broker configuration path triggered by that command. Compare the AdminBrokerThread log with the dashboard cluster→config flow. Done means fileReservedTime remains 168 instead of being replaced with the default 72.

Written by the indexing model from the issue text.