qemu-options.hx: Add zoom-to-fit to option summary for gtk

The detailed help lists zoom-to-fit as valid option but it is missing
from the short option summary. Add it there too.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

qemu-options.hx

@@ -2085,7 +2085,7 @@ DEF("display", HAS_ARG, QEMU_OPTION_display,
 #if defined(CONFIG_GTK)
     "-display gtk[,full-screen=on|off][,gl=on|off][,grab-on-hover=on|off]\n"
     "            [,show-tabs=on|off][,show-cursor=on|off][,window-close=on|off]\n"
-    "            [,show-menubar=on|off]\n"
+    "            [,show-menubar=on|off][,zoom-to-fit=on|off]\n"
 #endif
 #if defined(CONFIG_VNC)
     "-display vnc=<display>[,<optargs>]\n"