Drop duplicate display option documentation

The curses and none possibilities are already documented on a separate line,
so documenting it on the sdl line was both unneeded and confusing.

Introduced in commit f04ec5afSigned-off-by: NSamuel Thibault <samuel.thibault@ens-lyon.org>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

qemu-options.hx

@@ -926,7 +926,7 @@ ETEXI
 
 DEF("display", HAS_ARG, QEMU_OPTION_display,
     "-display sdl[,frame=on|off][,alt_grab=on|off][,ctrl_grab=on|off]\n"
-    "            [,window_close=on|off][,gl=on|off]|curses|none|\n"
+    "            [,window_close=on|off][,gl=on|off]\n"
     "-display gtk[,grab_on_hover=on|off][,gl=on|off]|\n"
     "-display vnc=<display>[,<optargs>]\n"
     "-display curses\n"