EmulatorPkg: Define default value of NETWORK_HTTP_ENABLE

BZ:https://bugzilla.tianocore.org/show_bug.cgi?id=3104
Incorporate with commit 126115a9, set default NETWORK_HTTP_ENABLE
to FALSE.

Signed-off-by: Abner Chang <abner.chang@hpe.com>

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Nickle Wang <nickle.wang@hpe.com>
Cc: Peter O'Hanley <peter.ohanley@hpe.com>
Acked-by: Ray Ni <ray.ni@intel.com>

EmulatorPkg/EmulatorPkg.dsc

@@ -32,6 +32,7 @@
   DEFINE NETWORK_IP6_ENABLE       = FALSE
   DEFINE NETWORK_TLS_ENABLE       = FALSE
   DEFINE NETWORK_HTTP_BOOT_ENABLE = FALSE
+  DEFINE NETWORK_HTTP_ENABLE      = FALSE
   DEFINE NETWORK_ISCSI_ENABLE     = FALSE
   DEFINE SECURE_BOOT_ENABLE       = FALSE