Throw expression with null-coalesce operator does not update the type of an array

# Bug report



When the `$array['x'] ?? throw new \Exception()` syntax is used, PHPStan should allow using the `'x'` key after that expression. It does not

### Code snippet that reproduces the problem

https://phpstan.org/r/62a2fe2c-78e5-41e5-982b-55ae5304d23a

### Expected output

No error.