Clarify the use of showstars in the docs.

doc/org.texi

@@ -8337,10 +8337,12 @@ the variable @code{org-hide-leading-stars} or change this on a per-file basis
 with
 
 @example
-#+STARTUP: showstars
 #+STARTUP: hidestars
 @end example
 
+@noindent
+Note that the opposite behavior is selected with @code{showstars}.
+
 With hidden stars, the tree becomes:
 
 @example