ci: change wrong php-version

Change php-version for code-style job.

#10

Author: josantonius

.github/workflows/ci.yml

@@ -21,7 +21,7 @@ jobs:
       - name: 'Setup PHP'
         uses: 'shivammathur/setup-php@v2'
         with:
-          php-version: '8.1'
+          php-version: '7.4'
           coverage: 'none'
           tools: 'composer:v2, composer-normalize'