ox-texinfo: Fix code typo

* lisp/ox-texinfo.el (org-texinfo--menu-entries): Only collect direct
  children.

The regression was introduced in
1b415735ea236a5e9dfff06428378b6ba5f9e80b.

lisp/ox-texinfo.el

@@ -1216,7 +1216,7 @@ holding contextual information."
 	       (cl-remove-if
 		(lambda (h)
 		  (org-not-nil (org-export-get-node-property :COPYING h t)))
-		(org-export-collect-headlines info nil scope))
+		(org-export-collect-headlines info 1 scope))
 	       cache))))
 
 ;;;; Node Property