Revert "WiFiSTA - allow using DHCP again after disconnecting static IP (espressif#8848)" (#297)

This reverts commit a9a72d1.

Co-authored-by: Juraj Andrassy <juraj.andrassy@gmail.com>

Author: Jason2866

libraries/WiFi/src/WiFiSTA.cpp

@@ -291,7 +291,6 @@ bool WiFiSTAClass::disconnect(bool wifioff, bool eraseap)
     wifi_sta_config(&conf);
 
     if(WiFi.getMode() & WIFI_MODE_STA){
-        _useStaticIp = false;
         if(eraseap){
             if(esp_wifi_set_config((wifi_interface_t)ESP_IF_WIFI_STA, &conf)){
                 log_e("clear config failed!");