Fix static call to instance methods in PHPUnit

Problem/Motivation

Drupal/Tests/Core/Render/RendererTest has a few PHPStan failures like

$ignoreErrors[] = [
	'message' => '#^Static call to instance method PHPUnit\\\\Framework\\\\TestCase\\:\\:exactly\\(\\)\\.$#',
	'identifier' => 'method.staticCall',
	'count' => 3,
	'path' => __DIR__ . '/tests/Drupal/Tests/Core/Render/RendererTest.php',
];

that are reported when PHPStan runs with PHPUnit 11 in place.

Proposed resolution

Fix.

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet