Provide test elastic 8 env

Author: harryzcy

.github/workflows/pull-db-tests.yml

@@ -67,6 +67,7 @@ jobs:
           TEST_LDAP: 1
           USE_REPO_TEST_DIR: 1
           TEST_INDEXER_CODE_ES_URL: "http://elastic:changeme@elasticsearch:9200"
+          TEST_ELASTICSEARCH_VERSION: 8
 
   test-sqlite:
     if: needs.files-changed.outputs.backend == 'true' || needs.files-changed.outputs.actions == 'true'