wip: clamp version for coverage

Author: Greg Bowler

.github/workflows/ci-coverage.yml

@@ -14,6 +14,7 @@ jobs:
       - name: PHPUnit Tests
         uses: php-actions/phpunit@v3
         with:
+          version: 9.5.26
           php_extensions: xdebug
           bootstrap: vendor/autoload.php
           configuration: test/phpunit.xml