ci: also run --prefer-lowest

Author: williamdes

.github/workflows/tests.yml

@@ -15,7 +15,7 @@ jobs:
                 php-version: ["7.2", "7.3", "7.4", "8.0", "8.1", "8.2", "8.3", "8.4", "8.5"]
                 os: [ubuntu-latest]
                 experimental: [false]
-                composer-options: ['']
+                composer-options: ['', '--prefer-lowest']
                 include:
                     - { php-version: 'nightly', composer-options: '--ignore-platform-req=php+', experimental: true, os: ubuntu-latest }
         steps: