Run static-analysis Github action on PHP 8.1 (#338)

Author: sirbrillig

.github/workflows/csqa.yml

@@ -91,7 +91,7 @@ jobs:
       - name: Install PHP
         uses: shivammathur/setup-php@v2
         with:
-          php-version: 'latest'
+          php-version: "8.1"
           coverage: none
 
       # Install dependencies and handle caching in one go.