New J2K: Fix incorrect testData (due to nullability bug in old j2k)

j2k/testData/fileOrElement/overloads/Private.new.kt

@@ -0,0 +1,6 @@
+internal class A {
+    private fun bar(s: String? = null): Int {
+        println("s = $s")
+        return 0
+    }
+}