Removed flush_synced (see opensearch-project/opensearch-clients#12)

Author: Robert Kaczmarczyk

src/DsOpenSearchBundle/Service/IndexPersistenceService.php

@@ -214,9 +214,6 @@ public function commit(string $commitMode = 'refresh', array $params = []): arra
             case 'flush':
                 $this->client->indices()->flush();
                 break;
-            case 'flush_synced':
-                $this->client->indices()->flushSynced();
-                break;
             case 'refresh':
                 $this->client->indices()->refresh();
                 break;