Update kotlin-tour-intermediate-scope-functions.md

error message is wrong, and String? isn't inferred type in this case

Author: Geek-Joe

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

@@ -74,7 +74,7 @@ the `sendNotification()` function because this function doesn't expect that `add
 The compiler reports an error as a result: 
 
 ```text
-Type mismatch: inferred type is String? but String was expected
+Argument type mismatch: actual type is 'String?', but 'String' was expected.
 ```
 
 From the beginner tour, you already know that you can perform a null check with an if condition or use the [Elvis operator `?:`](kotlin-tour-null-safety.md#use-elvis-operator). 
@@ -537,4 +537,4 @@ fun main() {
 
 ## Next step
 
-[Intermediate: Lambda expressions with receiver](kotlin-tour-intermediate-lambdas-receiver.md)
+[Intermediate: Lambda expressions with receiver](kotlin-tour-intermediate-lambdas-receiver.md)