GH Actions: run code coverage on PHP 8.0 again

Related to 245

Refs:
* sebastianbergmann/php-code-coverage 1025
* phpDocumentor/TypeResolver 197
* nikic/PHP-Parser 981

Author: jrfnl

.github/workflows/test.yml

@@ -164,7 +164,7 @@ jobs:
         include:
           - php: '7.2'
             custom_ini: false
-          - php: '8.1'
+          - php: '8.0'
             custom_ini: true
           - php: '8.3'
             custom_ini: false