Composer: update PHPUnit version constraints [1]

While PHPUnit as of version 8.5.12 allows for installation on PHP 8.0, it still contained a [nasty bug](sebastianbergmann/phpunit#4575) which would error out the test run with a Fatal when PHPUnit 8.5.12 would be installed for PHP 8.1.

This bug was fixed in version 8.5.14.

This adjustment of the version constraints means that when `composer install` is run with `--prefer-lowest` on PHP 8.x, PHPUnit 8.5.14 will be installed instead of PHP 8.5.12, while still allowing for all other 8.x versions in all other circumstances.

Ref: https://github.com/sebastianbergmann/phpunit/blob/8.5/ChangeLog-8.5.md

composer.json

@@ -32,7 +32,7 @@
         "antecedent/patchwork": "^2.1.17"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7.9 || ^6.0 || ^7.0 || ^8.0 || ^9.0",
+        "phpunit/phpunit": "^5.7.9 || ^6.0 || ^7.0 || >=8.0 <8.5.12 || ^8.5.14 || ^9.0",
         "phpcompatibility/php-compatibility": "^9.3.0",
         "dealerdirect/phpcodesniffer-composer-installer": "^0.6 || ^0.7"
     },