Duplication between section 2 and section 4

[cwoodall]

[adamgreen]

I welcomed this little bit of duplication during my first read through of this tutorial as a person new to embedded Rust. I found it useful to find the information in chapter 2 so early so that I knew what I had to order as I prepared to read the rest of the documentation later in the month. Chapter 2 is giving you a list of hardware that you will need to have on hand and chapter 4 is mostly just discussing the features of the STM32F3DISCOVERY board itself.

I will say that it seems like there is so little said about the serial and bluetooth modules in chapter 4, they could probably have been omitted.