N°3091 Update PHPUnit to 8.5 : fix setUp and teardDown methods signatures

"Return type declaration must be compatible with parent"
See https://phpunit.de/announcements/phpunit-8.html "Return Type of Template Methods"

test/integration/iTopModulesXmlVersionChecklistTest.php

@@ -29,7 +29,7 @@ use iTopDesignFormat;
  */
 class iTopModulesXmlVersionIntegrationTest extends ItopTestCase
 {
-	protected function setUp()
+	protected function setUp(): void
 	{
 		parent::setUp();