Fix LedgerAccount allowed_document_types type to accept bool

The Moneybird API can return a boolean for allowed_document_types
instead of an array. Updated the type from ?array to array|bool|null
to handle both cases.

Fixes TypeError in tests with PHP 8.2+ prefer-lowest.

Author: claude

src/Api/LedgerAccounts/LedgerAccount.php

@@ -15,7 +15,7 @@ public function __construct(
         public readonly ?string $account_type = null,
         public readonly ?string $account_id = null,
         public readonly ?bool $parent = null,
-        public readonly ?array $allowed_document_types = null,
+        public readonly array|bool|null $allowed_document_types = null,
         public readonly ?string $description = null,
         public readonly ?string $created_at = null,
         public readonly ?string $updated_at = null,