Sub: remove dead do_erase_logs method

ArduSub/Log.cpp

@@ -5,13 +5,6 @@
 // Code to Write and Read packets from DataFlash log memory
 // Code to interact with the user to dump or erase logs
 
-void Sub::do_erase_logs()
-{
-    gcs().send_text(MAV_SEVERITY_INFO, "Erasing logs");
-    DataFlash.EraseAll();
-    gcs().send_text(MAV_SEVERITY_INFO, "Log erase complete");
-}
-
 struct PACKED log_Optflow {
     LOG_PACKET_HEADER;
     uint64_t time_us;
@@ -364,7 +357,6 @@ void Sub::log_init()
 
 #else // LOGGING_ENABLED
 
-void Sub::do_erase_logs(void) {}
 void Sub::Log_Write_Control_Tuning() {}
 void Sub::Log_Write_Performance() {}
 void Sub::Log_Write_Attitude(void) {}

ArduSub/Sub.h

@@ -485,7 +485,6 @@ private:
     void send_pid_tuning(mavlink_channel_t chan);
     void gcs_data_stream_send(void);
     void gcs_update(void);
-    void do_erase_logs(void);
     void Log_Write_Optflow();
     void Log_Write_Control_Tuning();
     void Log_Write_Performance();