build: Update phpunit to fix PHP 7.3 build in CI

Started failing for some reason,
https://travis-ci.com/github/Krinkle/intuition/jobs/459494365

> PHP 7.3.25
> PHPUnit 8.4.3
>
> Use of undefined constant XDEBUG_CC_UNUSED - assumed 'XDEBUG_CC_UNUSED'
> (this will throw an Error in a future version of PHP)
>
> Script phpunit handling the test event returned with error code 2
> The command "composer test" exited with 2.
> Your build exited with 1.

composer.json

@@ -17,10 +17,10 @@
 		"php": ">=7.2"
 	},
 	"require-dev": {
-		"jakub-onderka/php-parallel-lint": "1.0.0",
-		"phpunit/phpunit": "^8.4.1",
+		"php-parallel-lint/php-parallel-lint": "^1.0.0",
+		"phpunit/phpunit": "^8.5.13",
 		"mediawiki/mediawiki-codesniffer": "28.0.0",
-		"php-coveralls/php-coveralls": "^2.1"
+		"php-coveralls/php-coveralls": "^2.4"
 	},
 	"scripts": {
 		"test": [