Use OPENSEARCH_JAVA_OPTS for opensearch

compose/env/opensearch.env

@@ -3,7 +3,7 @@ OPENSEARCH_PORT=9200
 OPENSEARCH_HEALTHCHECK_TIMEOUT=100
 
 ## Set custom heap size to avoid memory errors
-ES_JAVA_OPTS="-Xms1g -Xmx1g"
+OPENSEARCH_JAVA_OPTS="-Xms1g -Xmx1g"
 
 # Prevent security patch conflicts with core M2 code
 DISABLE_SECURITY_PLUGIN=true