### CI Link

only saw it locally

### Repro line

./gradlew ':server:test' --tests "org.elasticsearch.index.mapper.flattened.FlattenedFieldSearchTests.testCardinalityAggregation" -Dtests.seed=6E5A7D9AA8064CD5 -Dtests.locale=sr -Dtests.timezone=America/Campo_Grande -Druntime.java=18

### Does it reproduce?

Yes

### Applicable branches

master

### Failure history

_No response_

### Failure excerpt

```
REPRODUCE WITH: ./gradlew ':server:test' --tests "org.elasticsearch.index.mapper.flattened.FlattenedFieldSearchTests.testCardinalityAggregation" -Dtests.seed=EC78A8CA6F57105F -Dtests.locale=sv -Dtests.timezone=SystemV/MST7MDT -Druntime.java=18
  java.lang.AssertionError: 
    Expected: a value greater than <0L>
         but: <0L> was equal to <0L>
        at __randomizedtesting.SeedInfo.seed([EC78A8CA6F57105F:85146484AA481FC8]:0)
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
        at org.junit.Assert.assertThat(Assert.java:956)
        at org.junit.Assert.assertThat(Assert.java:923)
        at org.elasticsearch.index.mapper.flattened.FlattenedFieldSearchTests.assertCardinality(FlattenedFieldSearchTests.java:275)
        at org.elasticsearch.index.mapper.flattened.FlattenedFieldSearchTests.testCardinalityAggregation(FlattenedFieldSearchTests.java:249)
```

Reproduces every time for me locally. Will mute.

server/src/test/java/org/elasticsearch/index/mapper/flattened/FlattenedFieldSearchTests.java
assertCardinality(firstCount, numDocs, precisionThreshold);
        SearchResponse secondResponse = client().prepareSearch("test")
            .addAggregation(cardinality("cardinality").precisionThreshold(precisionThreshold).field("flattened.second"))
            .get();
        assertSearchResponse(secondResponse);
        Cardinality secondCount = secondResponse.getAggregations().get("cardinality");
        assertCardinality(secondCount, (numDocs + 1) / 2, precisionThreshold);
    }
    private void assertCardinality(Cardinality count, long value, int precisionThreshold) {
        if (value <= precisionThreshold) {
            
            assertEquals(value, count.getValue());
        } else {
            
            assertThat(count.getValue(), greaterThan(0L));
        }
    }
    public void testTermsAggregation() throws IOException {
        BulkRequestBuilder bulkRequest = client().prepareBulk("test").setRefreshPolicy(RefreshPolicy.IMMEDIATE);
        for (int i = 0; i < 5; i++) {
            bulkRequest.add(
                client().prepareIndex()
                    .setSource(
                        XContentFactory.jsonBuilder()
                            .startObject()
                            .startObject("labels")
                            .field("priority", "urgent")
                            .field("release", "v1.2." + i)
                            .endObject()
                            .endObject()