Update part6c.md - Fix capitalisation

Author: nikogenix

src/content/6/en/part6c.md

@@ -213,7 +213,7 @@ noteService.getAll().then(notes =>
 )
 ```
 
-> **NB:** why didn't we use await in place of promises and event handlers (registered to _then_-methods)?
+> **NB:** Why didn't we use await in place of promises and event handlers (registered to _then_-methods)?
 >
 > Await only works inside <i>async</i> functions, and the code in <i>index.js</i> is not inside a function, so due to the simple nature of the operation, we'll abstain from using <i>async</i> this time.