backend/tests: update and disable 'defaults4'

backend.native/tests/build.gradle

@@ -172,6 +172,7 @@ task defaults3(type: RunKonanTest) {
 }
 
 task defaults4(type: RunKonanTest) {
+    disabled = true
     goldValue = "43\n"
     source = "codegen/function/defaults4.kt"
 }

backend.native/tests/codegen/function/defaults4.kt

@@ -2,10 +2,12 @@ open class A {
     open fun foo(x: Int = 42) = println(x)
 }
 
-class B : A() {
+open class B : A()
+
+class C : B() {
     override fun foo(x: Int) = println(x + 1)
 }
 
 fun main(args: Array<String>) {
-    B().foo()
+    C().foo()
 }