Migrate testdata to new lambda syntax

js/js.translator/testData/expression/function/cases/adderClosure.kt

@@ -2,7 +2,7 @@ package foo
 
 fun box(): Boolean {
     var sum = 0
-    val adder = {(a: Int) -> sum += a }
+    val adder = { a: Int -> sum += a }
     adder(3)
     adder(2)
     return sum == 5