Bug 485661 - [1.8][null] bogus conflict reported between @NonNull type variable and its @Nullable upper bound

From https://bugs.eclipse.org/bugs/show_bug.cgi?id=485661

NTAT.testBinary06() expects this error:
```
public class X2<@NonNull W extends @Nullable Object> {}
^^^^^^^^^
This nullness annotation conflicts with a '@NonNull' annotation which is effective on the same type parameter
```

This doesn't make sense, since `extends @Nullable` imposes no restriction. The given snippet is meaningless, but not erroneous.