Update tests/explicit-nulls/pos/union-contains-contextual-function.scala

Co-authored-by: Ondřej Lhoták <[email protected]>

Author: noti0na1

tests/explicit-nulls/pos/union-contains-contextual-function.scala

@@ -1,6 +1,8 @@
 class Test:
   val x: ((a: String) ?=> Int) | Null = null
 
+  val x2: ((a: String) ?=> Int) | Null = (s: String) ?=> 42
+
   val y: ((a: String) ?=> Int) | String = "hello"
 
   def f(g: ((a: String) ?=> Int) | Null = null) = ???