ci: changed code coverage to run PHP 7.4 as scrutinizer doesn't support 8.0 yet

Author: LaravelFreelancerNL

.github/workflows/coverage.yml

@@ -26,7 +26,7 @@ jobs:
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 8.0
+          php-version: 7.4
           extensions: mbstring, intl
           ini-values: post_max_size=256M, short_open_tag=On
           coverage: xdebug