Run tests-code-coverage on PHP 8

Author: ondrejmirtes

.github/workflows/tests.yml

@@ -145,7 +145,7 @@ jobs:
         uses: "shivammathur/setup-php@v2"
         with:
           coverage: "pcov"
-          php-version: "7.4"
+          php-version: "8.0"
           tools: pecl
           extensions: ds