Minor improvements to morse-tutorial code. (#521)

Co-authored-by: Kasper Lund <kasper@toit.io>

Author: floitsch

docs/language/package/pkgtutorial.mdx

@@ -315,7 +315,7 @@ It assumes that pin 23 is connected to an LED (and an appropriate resistor).
 LED-PIN ::= 23
 
 main:
-  pin := gpio.Pin.out LED-PIN
+  pin := gpio.Pin --output LED-PIN
 
   10.repeat:
     morse-tutorial.emit