Bump phpunit/phpunit from 9.6.22 to 12.3.15

Bumps [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) from 9.6.22 to 12.3.15.
- [Release notes](https://github.com/sebastianbergmann/phpunit/releases)
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/12.3.15/ChangeLog-12.3.md)
- [Commits](sebastianbergmann/phpunit@9.6.22...12.3.15)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-version: 12.3.15
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

composer.json

@@ -53,7 +53,7 @@
     "require-dev": {
         "ext-json": "*",
         "mikey179/vfsstream": "^1.6.12",
-        "phpunit/phpunit": "^9.6.22"
+        "phpunit/phpunit": "^12.3.15"
     },
     "autoload-dev": {
         "psr-4": {