Update s3 pipeline env variable secret override

Author: joheec

.buildkite/release_central.yml

@@ -16,6 +16,7 @@ steps:
       env:
         DESTINATION_PATH: "s3://artifacts.elastic.co/javadoc/co/elastic/clients/elasticsearch-java/"
         EXTRACT_ARTIFACT: "elasticsearch-java-${VERSION}-javadoc.jar"
+        SECRET_OVERRIDE: "releasing"
         DRY_RUN: "true"
 
 #notify: