fix typo

Author: dzvon

src/05-led-roulette/the-challenge.md

@@ -63,7 +63,7 @@ break DefaultHandler
 # Set a breakpiont at HardFault
 break HardFault
 
-# Continue running and unill we hit the main breakpoint
+# Continue running and until we hit the main breakpoint
 continue
 
 # Step from the trampoline code in entry into main
@@ -149,4 +149,4 @@ the [embedded discovery book](https://github.com/rust-embedded/discovery) so you
 can save your changes in your own branch of your fork. We suggest creating
 your own branch and leaving the `master` branch alone so the `master` branch
 of your fork can stay in sync with the upstream repo. Also, it allows you to
-more easily create PR's and improve this book, **thank you in advance**!
+more easily create PR's and improve this book, **thank you in advance**!