Update kotlin-tour-functions.md

Remove Default argument

The Default argument is used here is confusing because it is explained in the next heading

docs/topics/tour/kotlin-tour-functions.md

@@ -71,7 +71,7 @@ you can write the parameters in any order.
 {type="tip"}
 
 ```kotlin
-fun printMessageWithPrefix(message: String, prefix: String = "Info") {
+fun printMessageWithPrefix(message: String, prefix: String) {
     println("[$prefix] $message")
 }