Public readonly properties are unset in Proxy's constructor

### Failing Test

| Q | A
|------------ | ------
| BC Break | no
| Version | 3.2.0

- https://github.com/doctrine/orm/issues/9432
- https://github.com/doctrine/orm/pull/9431

#### Summary

Public readonly properties are unset in Proxy's constructor, which results in error.

#### Current behavior

`Cannot unset readonly property \Entity\SimpleBook::$title from scope Proxies\__CG__\Entity\SimpleBook`

#### How to reproduce

```php
#[Entity, Table]
class SimpleBook
{
#[Column, Id, GeneratedValue]
private readonly int $id;

#[Column]
public readonly string $title;

#[ManyToOne, JoinColumn(nullable: false)]
private readonly Author $author;

public function getId(): int
{
return $this->id;
}

public function getTitle(): string
{
return $this->title;
}

public function getAuthor(): Author
{
return $this->author;
}
}

class SimpleBook extends \Entity\SimpleBook implements \Doctrine\ORM\Proxy\Proxy
{
// ...

public function __construct(?\Closure $initializer = null, ?\Closure $cloner = null)
{
unset($this->title);

$this->__initializer__ = $initializer;
$this->__cloner__ = $cloner;
}
}
```

#### Expected behavior

#### Code that generates Proxy's constructor

I dug into ProxyGenerator and here is generation of these unsets:

- https://github.com/doctrine/common/blob/3.2.x/lib/Doctrine/Common/Proxy/ProxyGenerator.php#L979

`public readonly ` properties are not tested as I see in tests.

- https://github.com/doctrine/common/blob/3.2.x/tests/Doctrine/Tests/Common/Proxy/ProxyGeneratorTest.php#L481