fix(nan): set group_mgmt_prot in WIFI_NAN_SYNC_CONFIG_DEFAULT

The default initializer explicitly sets every other bool field but omitted
the new group_mgmt_prot, leaving the intended default ambiguous. Set it to
false so the macro stays exhaustive; both example apps use it.

components/esp_wifi/wifi_apps/nan_app/include/esp_nan.h

@@ -24,6 +24,7 @@ extern "C" {
     .disable_random_mac = false, \
     .reset_current_nvs_creds = false, \
     .use_nvs_for_caching = false, \
+    .group_mgmt_prot = false, \
 };
 
 #define NDP_STATUS_ACCEPTED     1