Update dependency phpstan/phpstan to v1.12.15 (#4345)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [phpstan/phpstan](https://redirect.github.com/phpstan/phpstan) |
`1.12.14` -> `1.12.15` |
[![age](https://developer.mend.io/api/mc/badges/age/packagist/phpstan%2fphpstan/1.12.15?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/packagist/phpstan%2fphpstan/1.12.15?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/packagist/phpstan%2fphpstan/1.12.14/1.12.15?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/packagist/phpstan%2fphpstan/1.12.14/1.12.15?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>phpstan/phpstan (phpstan/phpstan)</summary>

###
[`v1.12.15`](https://redirect.github.com/phpstan/phpstan/releases/tag/1.12.15)

[Compare
Source](https://redirect.github.com/phpstan/phpstan/compare/1.12.14...1.12.15)

# Bugfixes 🐛

- Fix inferring type of `new` with generic type with constructor in
parent class
(phpstan/phpstan-src@a063119),
[#&#8203;8219](https://redirect.github.com/phpstan/phpstan/issues/8219),
[#&#8203;2735](https://redirect.github.com/phpstan/phpstan/issues/2735)
- Support tagged unions in `array_merge`
([#&#8203;3770](https://redirect.github.com/phpstan/phpstan-src/pull/3770)),
[#&#8203;7857](https://redirect.github.com/phpstan/phpstan/issues/7857),
[#&#8203;8632](https://redirect.github.com/phpstan/phpstan/issues/8632),
[#&#8203;9559](https://redirect.github.com/phpstan/phpstan/issues/9559),
thanks [@&#8203;herndlm](https://redirect.github.com/herndlm)!

# Internals 🔍

- Cleanup `instanceof ConstantBooleanType` checks
([#&#8203;3771](https://redirect.github.com/phpstan/phpstan-src/pull/3771)),
thanks [@&#8203;staabm](https://redirect.github.com/staabm)!

</details>

---

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Author: renovate[bot]

composer.json

@@ -63,7 +63,7 @@
         "dama/doctrine-test-bundle": "8.2.0",
         "ergebnis/composer-normalize": "2.45.0",
         "friendsofphp/php-cs-fixer": "3.65.0",
-        "phpstan/phpstan": "1.12.14",
+        "phpstan/phpstan": "1.12.15",
         "phpstan/phpstan-doctrine": "1.5.7",
         "phpstan/phpstan-phpunit": "1.4.2",
         "phpstan/phpstan-symfony": "1.4.13",