build: exclude a workaround for VTE/Konsole when using a recent ncurses

The workaround was for https://savannah.gnu.org/bugs/?51335
(a cursor-misplacement bug), but both an recent Xfce Terminal
and a recent Konsole appear unaffected by the issue.  So, drop
the workaround for modern systems.

src/winio.c

@@ -2131,9 +2131,11 @@ void statusline(message_type importance, const char *msg, ...)
 		waddstr(bottomwin, " ]");
 	wattroff(bottomwin, colorpair);
 
+#ifdef USING_OLDER_LIBVTE
 	/* Defeat a VTE/Konsole bug, where the cursor can go off-limits. */
 	if (ISSET(CONSTANT_SHOW) && ISSET(NO_HELP))
 		wmove(bottomwin, 0, 0);
+#endif
 
 	/* Push the message to the screen straightaway. */
 	wrefresh(bottomwin);