Added select to client warnings

Author: ArneTR

content/en/docs/cluster/security.md

@@ -136,7 +136,7 @@ GRANT USAGE, SELECT ON SEQUENCE phase_stats_id_seq TO client;
 GRANT INSERT on changelog to client;
 GRANT SELECT, USAGE on changelog_id_seq to client;
 
-GRANT INSERT on warnings to client;
+GRANT SELECT,INSERT on warnings to client;
 GRANT SELECT, USAGE on warnings_id_seq to client;
 
 ```