Revert "WiFiSTA - allow using DHCP again after disconnecting static IP (espressif#8848)" (espressif#8873)

This reverts commit a9a72d1. Co-authored-by: Rodrigo Garcia <rodrigo.garcia@espressif.com>

Author: JAndrassy

libraries/WiFi/src/WiFiSTA.cpp

@@ -373,7 +373,6 @@ 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!");