[ub:basic.stc.alloc.dealloc.constraint] Irrelevant UB example

Currently it says

```cpp
void operator delete(void* ptr) noexcept {
    throw 0;                // undefined behavior, terminates by throwing an exception
}
```

[basic.stc.dynamic.deallocation]/3 merely says

> ... A deallocation function shall not have a potentially throwing exception specification. ...

The "throwing an exception in a noexcept function" example is irrelevant for this UB.