Fixed KT-5434 J2K: incorrect conversion of main method

#KT-5434 Fixed

j2k/tests/testData/ast/function/mainAndNullabilitySetting.java

@@ -0,0 +1,6 @@
+// !forceNotNullTypes: false
+//file
+public class A {
+    public static void main(String[] args) {
+    }
+}