Fix help string to disable xpresent

Bug: 11857

Reported-by:  <pomidorabelisima@gmail.com>
Signed-off-by: Olivier Fourdan <fourdan@xfce.org>

configure.ac.in

@@ -192,7 +192,7 @@ dnl XPresent support
 dnl
 AC_ARG_ENABLE([xpresent],
 AC_HELP_STRING([--enable-xpresent], [try to use the xpresent extension])
-AC_HELP_STRING([--disable-render], [don't try to use the xpresent extension]),
+AC_HELP_STRING([--disable-xpresent], [don't try to use the xpresent extension]),
   [], [enable_xpresent=yes])
 have_xpresent="no"
 XPRESENT_LIBS=