WiFi: fix memory leak in scanNetworks()

Author: pennam

libraries/WiFi/src/WiFi.cpp

@@ -215,7 +215,8 @@ int8_t arduino::WiFiClass::scanNetworks() {
   connected_ap = SSID_MAX_COUNT;
   uint8_t count = SSID_MAX_COUNT;
   if (ap_list != nullptr) {
-    free(ap_list);
+    delete[]ap_list;
+    ap_list = nullptr;
   }
   ap_list = new WiFiAccessPoint[count];
   return wifi_if->scan(ap_list, count);