Removed unused variable

Author: PilnyTomas

libraries/I2S/src/I2S.cpp

@@ -988,7 +988,6 @@ void I2SClass::_post_read_data_fix(void *input, size_t *size){
 // bytes_written - number of bytes used from original buffer
 // actual_bytes_written - number of bytes written by i2s_write after fix
 void I2SClass::_fix_and_write(void *output, size_t size, size_t *bytes_written, size_t *actual_bytes_written){
-  long start = millis();
   ulong src_ptr = 0;
   uint8_t* buff = NULL;
   size_t buff_size = size;