hw/i386/pc: Remove unused pc_compat_2_3 declarations

We removed the implementations in commit 46a2bd52571
("hw/i386/pc: Remove deprecated pc-i440fx-2.3 machine")
but forgot to remove the declarations. Do it now.

Fixes: 46a2bd52571 ("hw/i386/pc: Remove deprecated pc-i440fx-2.3 machine")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Michael Tokarev <mjt@tls.msk.ru>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

include/hw/i386/pc.h

@@ -302,9 +302,6 @@ extern const size_t pc_compat_2_5_len;
 extern GlobalProperty pc_compat_2_4[];
 extern const size_t pc_compat_2_4_len;
 
-extern GlobalProperty pc_compat_2_3[];
-extern const size_t pc_compat_2_3_len;
-
 #define DEFINE_PC_MACHINE(suffix, namestr, initfn, optsfn) \
     static void pc_machine_##suffix##_class_init(ObjectClass *oc, void *data) \
     { \