precision for hook script stdout/stderr displayed as logs

See also corresponding issue on main lsc project:
lsc-project/lsc#262

source/syncrules.rst

@@ -152,7 +152,7 @@ In this node, you can call a hook for each specific operations:
 * ``deletePostHook``: path to the hook script managing each entry removal. The script will be called with 2 arguments: the DN of the entry, and the operation (``delete``). Nothing is passed on stdin.
 * ``changeIdPostHook``: path to the hook script managing each entry renaming. The script will be called with 2 arguments: the DN of the entry, and the operation. The entry is passed on stdin, in the appropriate ``outputformat``
 
-Hook scripts are not supposed to write anything to stdout or stderr. If so, LSC will display theses messages as log warnings.
+Messages sent by the hook script on stdout are displayed as logs at level INFO. Messages sent by the hook script on stderr are displayed as logs at level ERROR.
 
 Here is an example of modification in ldif, passed to stdin: