Update PHPStan packages

| datasource | package                           | from    | to     |
| ---------- | --------------------------------- | ------- | ------ |
| packagist  | phpstan/extension-installer       | 1.2.0   | 1.4.3  |
| packagist  | phpstan/phpstan                   | 1.10.38 | 1.12.6 |
| packagist  | phpstan/phpstan-deprecation-rules | 1.1.4   | 1.2.1  |
| packagist  | phpstan/phpstan-phpunit           | 1.3.15  | 1.4.0  |
| packagist  | phpstan/phpstan-strict-rules      | 1.5.1   | 1.6.1  |

Author: renovate[bot]