WiFiClient: removing unimplemented method

Author: andreagilardoni

libraries/WiFiS3/src/WiFiClient.h

@@ -77,7 +77,6 @@ class WiFiClient : public Client {
   std::shared_ptr<FifoBuffer<uint8_t,RX_BUFFER_DIM>> rx_buffer;
   int _read();
   void read_if_needed(size_t s);
-  void clear_buffer();
   bool destroy_at_distructor;