Update dependency phpunit/phpunit to v9.6.9

| datasource | package         | from  | to    |
| ---------- | --------------- | ----- | ----- |
| packagist  | phpunit/phpunit | 9.6.8 | 9.6.9 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

composer.json

@@ -20,7 +20,7 @@
     },
     "require-dev": {
         "laminas/laminas-coding-standard": "~2.5.0",
-        "phpunit/phpunit": "9.6.8",
+        "phpunit/phpunit": "9.6.9",
         "psalm/plugin-phpunit": "^0.18.0",
         "roave/security-advisories": "dev-master",
         "vimeo/psalm": "^5.0.0"