Update phpunit/phpunit requirement from ^9 to ^10 (#3)

* Update phpunit/phpunit requirement from ^9 to ^10

Updates the requirements on [phpunit/phpunit](https://github.com/sebastianbergmann/phpunit) to permit the latest version.
- [Changelog](https://github.com/sebastianbergmann/phpunit/blob/10.1.3/ChangeLog-10.1.md)
- [Commits](sebastianbergmann/phpunit@9.0.0...10.1.3)

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

* Just PHPUnit 10

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Jesse Donat <donatj@gmail.com>

composer.json

@@ -15,7 +15,7 @@
 	"require-dev": {
 		"donatj/drop": "^1.1",
 		"donatj/mddoc": "^0.7.0",
-		"phpunit/phpunit": "^9",
+		"phpunit/phpunit": "^10",
 		"friendsofphp/php-cs-fixer": "^3.16",
 		"corpus/coding-standard": "^0.7.0",
 		"slevomat/coding-standard": "^8.11",