Fix call_user_func parameter name for PHP 7.4 compatibility

The first parameter of call_user_func is named $function in PHP 7.x
but was renamed to $callback in PHP 8.0+. Use PHP_VERSION_ID to
select the correct name in the test assertion.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

tests/PHPStan/Rules/Functions/CallToFunctionParametersRuleTest.php

@@ -2819,9 +2819,10 @@ public function testBug14312b(): void
 
 	public function testBug4608(): void
 	{
+		$paramName = PHP_VERSION_ID >= 80000 ? 'callback' : 'function';
 		$this->analyse([__DIR__ . '/data/bug-4608-call-user-func.php'], [
 			[
-				"Parameter #1 \$callback of function call_user_func expects callable(): mixed, array{class@anonymous/tests/PHPStan/Rules/Functions/data/bug-4608-call-user-func.php:5, 'abc'|'not_abc'} given.",
+				"Parameter #1 \${$paramName} of function call_user_func expects callable(): mixed, array{class@anonymous/tests/PHPStan/Rules/Functions/data/bug-4608-call-user-func.php:5, 'abc'|'not_abc'} given.",
 				11,
 			],
 		]);