Directly call a callable containing string with 'Class::func' (fixes #60687)

```php
class MyClass {
    public static function myStaticFunc() {
        var_dump(__METHOD__);
    }
}

function call(callable $func) {
    $func();
}

$callFunction = 'call';
$callFunction('myclass::myStaticFunc');

$callFunction = 'myclass::myStaticFunc';
$callFunction();

$callFunction = 'myclass::unkownFunc';
$callFunction();
```

*BEFORE:*
The `callable` type-hint matches the given static method but it's not callable directly.
```
Fatal error: Call to undefined function myclass::myStaticFunc() in %s on line %d
```

*AFTER:*
```
string(21) "MyClass::myStaticFunc"
string(21) "MyClass::myStaticFunc"

Fatal error: Call to undefined method MyClass::unkownFunc() in %s on line %d
```

This should fix #60687, too.