Use PHP 8.1 for phpDocumentor

Author: takano32

.github/workflows/deploy-apidocs.yml

@@ -43,7 +43,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: '8.0'
+          php-version: '8.1'
           tools: phive
           coverage: none