Fix OpenSearch CI service configuration

Author: stevebauman

.github/workflows/run-tests.yml

@@ -13,7 +13,7 @@ jobs:
         image: opensearchproject/opensearch:2.13.0
         env:
           discovery.type: single-node
-          plugins.security.disabled: true
+          DISABLE_SECURITY_PLUGIN: true
           OPENSEARCH_JAVA_OPTS: -Xms512m -Xmx512m
         ports:
           - 9200:9200