Tests: fix GeoHashGridAggregatorTests expectations (#23556)

Currently GeoHashGridAggregatorTests#testWithSeveralDocs increases the expected
document count per hash for each geo point added to a document. When points
added to the same doc fall into one bucket (one hash cell) the document should
only be counted once.

Closes #23555

core/src/test/java/org/elasticsearch/search/aggregations/bucket/geogrid/GeoHashGridAggregatorTests.java

@@ -36,8 +36,10 @@ import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Consumer;
 
 import static org.elasticsearch.common.geo.GeoHashUtils.stringEncode;
@@ -68,15 +70,20 @@ public class GeoHashGridAggregatorTests extends AggregatorTestCase {
         Map<String, Integer> expectedCountPerGeoHash = new HashMap<>();
         testCase(new MatchAllDocsQuery(), FIELD_NAME, precision, iw -> {
             List<LatLonDocValuesField> points = new ArrayList<>();
+            Set<String> distinctHashesPerDoc = new HashSet<>();
             for (int pointId = 0; pointId < numPoints; pointId++) {
                 double lat = (180d * randomDouble()) - 90d;
                 double lng = (360d * randomDouble()) - 180d;
                 points.add(new LatLonDocValuesField(FIELD_NAME, lat, lng));
                 String hash = stringEncode(lng, lat, precision);
-                expectedCountPerGeoHash.put(hash, expectedCountPerGeoHash.getOrDefault(hash, 0) + 1);
+                if (distinctHashesPerDoc.contains(hash) == false) {
+                    expectedCountPerGeoHash.put(hash, expectedCountPerGeoHash.getOrDefault(hash, 0) + 1);
+                }
+                distinctHashesPerDoc.add(hash);
                 if (usually()) {
                     iw.addDocument(points);
                     points.clear();
+                    distinctHashesPerDoc.clear();
                 }
             }
             if (points.size() != 0) {