MDL-63892 mod_forum: Correction to timestamp added to edit strings

mod/forum/post.php

@@ -593,7 +593,7 @@ file_prepare_draft_area($draftitemid, $modcontext->id, 'mod_forum', 'attachment'
 
 if ($USER->id != $post->userid) {   // Not the original author, so add a message to the end.
     $data = new stdClass();
-    $data->date = userdate($post->modified);
+    $data->date = userdate($post->created);
     if ($post->messageformat == FORMAT_HTML) {
         $data->name = '<a href="'.$CFG->wwwroot.'/user/view.php?id='.$USER->id.'&course='.$post->course.'">'.
             fullname($USER).'</a>';