Add missing use statement for array_slice in Php8SignatureMapProvider

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

Author: phpstan-bot

src/Reflection/SignatureMap/Php8SignatureMapProvider.php

@@ -29,6 +29,7 @@
 use ReflectionFunctionAbstract;
 use function array_key_exists;
 use function array_map;
+use function array_slice;
 use function count;
 use function explode;
 use function is_string;