Modify LED control instructions in index.mdx (#660)

* Modify LED control instructions in index.mdx

Updated instructions to set the LED to LOW and added a note about using a loop.

* Clearer explanation

Co-authored-by: Alexandru Radovici <msg4alex@gmail.com>

---------

Co-authored-by: Alexandru Radovici <msg4alex@gmail.com>

Author: AurasV

website/lab/02/index.mdx

@@ -820,7 +820,12 @@ display-inlay-hints = true
 :::
 
 
-2. Write a program using Embassy that set on HIGH the LED connected to IO/D8 (PC7). (**1p**)
+2. Write a program using Embassy that set on LOW the LED connected to IO/D8 (PC7). (**1p**)
+
+:::note
+
+Please make sure you to put a `loop {}` at the end of the `main` function, otherwise Embassy will reset the
+pins at the end of the function and you will not see the LED turn on.
 
 :::danger