Dates Created from Strings with Timezone Offsets Aren't Properly Formatted When Using 'p'

### Description

The following code:

```php
<?php
$date = new \DateTimeImmutable('2023-01-25T00:00:00+00:00');
echo $date->format('Y-m-d\TH:i:sp');
```

Resulted in this output:
```
2023-01-25T00:00:00+00:00
```

But I expected this output instead:
```
2023-01-25T00:00:00Z
```


### PHP Version

8.2.1

### Operating System

MacOS Monterey (12.6.3)