Java to Kotlin converter: correct nullability in signatures of overrides

#KT-5269 Fixed

j2k/tests/testData/ast/nullability/OverrideWithInheritanceLoop.java

@@ -0,0 +1,8 @@
+//file
+class A extends B {
+    public void foo(String s) {}
+}
+
+class B extends A {
+    public void foo(String s) {}
+}