Import array_filter via use function

Satisfies SlevomatCodingStandard.Namespaces.ReferenceUsedNamesOnly —
follow-up to the previous commit which added an `array_filter` call
without a matching `use function` statement.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: gnutix

src/Type/TypeCombinator.php

@@ -27,6 +27,7 @@
 use PHPStan\Type\Generic\TemplateTypeFactory;
 use PHPStan\Type\Generic\TemplateUnionType;
 use function array_fill;
+use function array_filter;
 use function array_key_exists;
 use function array_key_first;
 use function array_merge;