Update backward-compatibility.yml

Author: staabm

.github/workflows/backward-compatibility.yml

@@ -25,7 +25,7 @@ jobs:
         uses: "shivammathur/setup-php@v2"
         with:
           coverage: "none"
-          php-version: "7.4"
+          php-version: "8.3"
 
       - name: "Install dependencies"
         run: "composer install --no-dev --no-interaction --no-progress --no-suggest"