### 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
TermsAggregationBuilder releaseAgg = createTermsAgg("labels.release");
        SearchResponse releaseResponse = client().prepareSearch("test").addAggregation(releaseAgg).get();
        assertSearchResponse(releaseResponse);
        Terms releaseTerms = releaseResponse.getAggregations().get("terms");
        assertThat(releaseTerms, notNullValue());
        assertThat(releaseTerms.getName(), equalTo("terms"));
        assertThat(releaseTerms.getBuckets().size(), equalTo(5));
        for (Terms.Bucket bucket : releaseTerms.getBuckets()) {
            assertThat(bucket.getKeyAsString(), startsWith("v1.2."));
            assertEquals(1, bucket.getDocCount());
        }
        
        TermsAggregationBuilder minDocCountAgg = createTermsAgg("labels.priority").minDocCount(0);
        SearchResponse minDocCountResponse = client().prepareSearch("test").addAggregation(minDocCountAgg).get();
        assertSearchResponse(minDocCountResponse);
        Terms minDocCountTerms = minDocCountResponse.getAggregations().get("terms");
        assertThat(minDocCountTerms, notNullValue());
        assertThat(minDocCountTerms.getName(), equalTo("terms"));
        assertThat(minDocCountTerms.getBuckets().size(), equalTo(1));
    }
    private TermsAggregationBuilder createTermsAgg(String field) {
        TermsAggregatorFactory.ExecutionMode executionMode = randomFrom(TermsAggregatorFactory.ExecutionMode.values());
        Aggregator.SubAggCollectionMode collectionMode = randomFrom(Aggregator.SubAggCollectionMode.values());
        return terms("terms").field(field).collectMode(collectionMode).executionHint(executionMode.toString());
    }
    public void testLoadDocValuesFields() throws Exception {
        client().prepareIndex("test")
            .setId("1")
            .setRefreshPolicy(RefreshPolicy.IMMEDIATE)