mod_pubsub: Move a comment to where it makes sense

This code has moved but the comment did not follow it.

plugins/mod_pubsub/mod_pubsub.lua

@@ -82,7 +82,6 @@ function simple_broadcast(kind, node, jids, item, actor, node_obj)
 	end
 
 	local summary;
-	-- Compose a sensible textual representation of at least Atom payloads
 	if item and item.tags[1] then
 		local payload = item.tags[1];
 		summary = module:fire_event("pubsub-summary/"..payload.attr.xmlns, {
@@ -116,6 +115,7 @@ function is_item_stanza(item)
 	return st.is_stanza(item) and item.attr.xmlns == xmlns_pubsub and item.name == "item";
 end
 
+-- Compose a textual representation of Atom payloads
 module:hook("pubsub-summary/http://www.w3.org/2005/Atom", function (event)
 	local payload = event.payload;
 	local title = payload:get_child_text("title");