remove unnecessary if branch

checking `length` in below while statement

Author: zakkie

cores/arduino/Stream.cpp

@@ -218,7 +218,6 @@ size_t Stream::readBytes(char *buffer, size_t length)
 
 size_t Stream::readBytesUntil(char terminator, char *buffer, size_t length)
 {
-  if (length < 1) return 0;
   size_t index = 0;
   while (index < length) {
     int c = timedRead();