chore(deps): update dependency phpunit/phpunit to v11.5.20 (#856)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [phpunit/phpunit](https://phpunit.de/)
([source](https://redirect.github.com/sebastianbergmann/phpunit)) |
`11.5.19` -> `11.5.20` |
[![age](https://developer.mend.io/api/mc/badges/age/packagist/phpunit%2fphpunit/11.5.20?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/packagist/phpunit%2fphpunit/11.5.20?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/packagist/phpunit%2fphpunit/11.5.19/11.5.20?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/packagist/phpunit%2fphpunit/11.5.19/11.5.20?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>sebastianbergmann/phpunit (phpunit/phpunit)</summary>

###
[`v11.5.20`](https://redirect.github.com/sebastianbergmann/phpunit/releases/tag/11.5.20):
PHPUnit 11.5.20

[Compare
Source](https://redirect.github.com/sebastianbergmann/phpunit/compare/11.5.19...11.5.20)

##### Fixed

-
[#&#8203;6199](https://redirect.github.com/sebastianbergmann/phpunit/issues/6199):
`assertEmpty()` and `assertNotEmpty()` use overly restrictive
`phpstan-assert empty` directives
-
[#&#8203;6192](https://redirect.github.com/sebastianbergmann/phpunit/issues/6192):
Reverted change made in PHPUnit 11.5.19 due to regression

***

[How to install or update
PHPUnit](https://docs.phpunit.de/en/11.5/installation.html)

</details>

---

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