Fix primitive override problem in Kotlin-Java inheritance

See the comment in JetTypeMapper

compiler/testData/compileJavaAgainstKotlin/method/primitiveOverride/NullableIntOverridesObject.kt

@@ -0,0 +1,9 @@
+trait A<T> {
+    fun foo(): T
+}
+
+open class B : A<Int?> {
+    override fun foo(): Int? = 42
+}
+
+abstract class C : A<Int?>