LibMarkdown: Have one newline between lists in terminal renders

Before this patch the markdown lists would have two space inbetween each
item. This patch removes one of these newlines for a nicer render.

Userland/Libraries/LibMarkdown/List.cpp

@@ -48,7 +48,6 @@ String List::render_for_terminal(size_t) const
         else
             builder.append("* ");
         builder.append(item->render_for_terminal());
-        builder.append("\n");
     }
     builder.append("\n");