Bump espressif8266 to 4.1.0

need to check this:
src/ESP-FTP-Server-Lib.cpp: In member function 'void FTPServer::handle()':
src/ESP-FTP-Server-Lib.cpp:47:114: warning: 'WiFiClient WiFiServer::available(uint8_t*)' is deprecated: Renamed to accept(). [-Wdeprecated-declarations]
   47 |   std::shared_ptr<FTPConnection> connection = std::shared_ptr<FTPConnection>(new FTPConnection(_Server.available(), _UserList, _Filesystem));
      |                                                                                                                  ^
In file included from src/FTPConnection.h:5,
                 from src/ESP-FTP-Server-Lib.h:8,
                 from src/ESP-FTP-Server-Lib.cpp:1:
/Users/pbuchegger/.platformio/packages/framework-arduinoespressif8266/libraries/ESP8266WiFi/src/WiFiServer.h:85:14: note: declared here
   85 |   WiFiClient available(uint8_t* status = NULL) __attribute__((deprecated("Renamed to accept().")));
      |              ^~~~~~~~~
In file included from src/FTPConnection.cpp:19:
src/Commands/STOR.h: In member function 'virtual void STOR::workOnData()':
src/Commands/STOR.h:46:11: warning: comparison of integer expressions of different signedness: 'const unsigned int' and 'int' [-Wsign-compare]
   46 |    if (wb != nb)
      |        ~~~^~~~~
Compiling .pio/build/ttgo-ESP8266/libb56/ESP8266WiFi/WiFiClientSecureBearSSL.cpp.o
Compiling .pio/build/ttgo-ESP8266/libb56/ESP8266WiFi/WiFiServer.cpp.o
In file included from src/FTPFilesystem.cpp:5:
src/FTPFilesystem.h: In member function 'virtual const char* FTPFileImpl::fullName() const':
src/FTPFilesystem.h:78:69: warning: function may return address of local variable [-Wreturn-local-addr]
   78 |     const char* fullName() const override {return ("/"+_Name).c_str();};
      |                                                                     ^
src/FTPFilesystem.h:78:56: note: declared here
   78 |     const char* fullName() const override {return ("/"+_Name).c_str();};
      |                                                        ^~~~~
Compiling .pio/build/ttgo-ESP8266/libb56/ESP8266WiFi/WiFiServerSecureBearSSL.cpp.o
src/test.cpp: In function 'void setup()':
src/test.cpp:33:2: warning: 'SPIFFS' is deprecated: SPIFFS has been deprecated. Please consider moving to LittleFS or other filesystems. [-Wdeprecated-declarations]
   33 |  SPIFFS.begin();
      |  ^~~~~~
In file included from src/test.cpp:6:
/Users/pbuchegger/.platformio/packages/framework-arduinoespressif8266/cores/esp8266/FS.h:286:15: note: declared here
  286 | extern fs::FS SPIFFS __attribute__((deprecated("SPIFFS has been deprecated. Please consider moving to LittleFS or other filesystems.")));
      |               ^~~~~~
src/test.cpp:53:31: warning: 'SPIFFS' is deprecated: SPIFFS has been deprecated. Please consider moving to LittleFS or other filesystems. [-Wdeprecated-declarations]
   53 |  ftp.addFilesystem("SPIFFS", &SPIFFS);
      |                               ^~~~~~
In file included from src/test.cpp:6:
/Users/pbuchegger/.platformio/packages/framework-arduinoespressif8266/cores/esp8266/FS.h:286:15: note: declared here
  286 | extern fs::FS SPIFFS __attribute__((deprecated("SPIFFS has been deprecated. Please consider moving to LittleFS or other filesystems.")));
      |               ^~~~~~
peterus / ESP-FTP-Server-Lib

Bump espressif8266 to 4.1.0 #25
