Add a missing seen_disp_event for ESC # 3 and friends.

These escape sequences immediately change the display of the line
they're invoked on, so they need to trigger a display update. But they
weren't, and I suppose we must have never noticed before due to the
complete confusion fixed in commit bdbd5f429c.

terminal/terminal.c

@@ -4223,6 +4223,7 @@ static void term_out(Terminal *term, bool called_from_term_data)
                     check_line_size(term, ldata);
                     check_trust_status(term, ldata);
                     ldata->lattr = nlattr;
+                    seen_disp_event(term);
                     break;
                   }
                   /* GZD4: G0 designate 94-set */