correct bounds checking in Print::printf to avoid corner case of len=64 (#2204)

Author: atanisoft

cores/esp32/Print.cpp

@@ -63,7 +63,7 @@ size_t Print::printf(const char *format, ...)
  len = vsnprintf(temp, len+1, format, arg);
 write((uint8_t*)temp, len);
 va_end(arg);
-if(len >64){
+if(len >= sizeof(loc_buf)){
 delete[] temp;
  }
 return len;