use Elasticsearch 6 in default

packages/app/.env.development

@@ -13,8 +13,6 @@ MONGO_URI="mongodb://mongo:27017/growi"
 # NCHAN_URI="http://nchan"
 ELASTICSEARCH_URI="http://elasticsearch:9200/growi"
 ELASTICSEARCH_REQUEST_TIMEOUT=15000
-ELASTICSEARCH_REJECT_UNAUTHORIZED=false
-USE_ELASTICSEARCH_V6=false
 HACKMD_URI="http://localhost:3010"
 HACKMD_URI_FOR_SERVER="http://hackmd:3000"
 # DRAWIO_URI="http://localhost:8080/?offline=1&https=0"

packages/app/src/server/service/config-loader.ts

@@ -314,7 +314,7 @@ const ENV_VAR_NAME_TO_CONFIG_INFO = {
     ns:      'crowi',
     key:     'app:useElasticsearchV6',
     type:    ValueType.BOOLEAN,
-    default: false,
+    default: true,
   },
   MONGO_GRIDFS_TOTAL_LIMIT: {
     ns:      'crowi',