occasional TestMonitorReadonly.testReadonlyMonitorGetsRefreshed failure

### Description

e.g. see https://lists.apache.org/list?builds@lucene.apache.org:lte=1M:%22org.apache.lucene.monitor.TestMonitorReadonly.testReadonlyMonitorGetsRefreshed%22

```
Stack Trace:
java.lang.AssertionError
at __randomizedtesting.SeedInfo.seed([BD813153873A7E63:8B8B307BB814AC97]:0)
at junit@4.13.1/org.junit.Assert.fail(Assert.java:87)
at junit@4.13.1/org.junit.Assert.assertTrue(Assert.java:42)
at junit@4.13.1/org.junit.Assert.assertTrue(Assert.java:53)
at org.apache.lucene.monitor.TestMonitorReadonly.testReadonlyMonitorGetsRefreshed(TestMonitorReadonly.java:216)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
...
```

### Gradle command to reproduce

_No response_

Start with org.apache.lucene.monitor.TestMonitorReadonly.testReadonlyMonitorGetsRefreshed at line 216 and the linked failure reports. Run the named test repeatedly to characterize the intermittent assertion failure; no Gradle reproduction command is provided. Done means the failure is understood and the test passes reliably.

Written by the indexing model from the issue text.