ci: fix and upgrade workflow

Author: DannyvdSluijs

.github/workflows/main.yml

@@ -79,6 +79,7 @@ jobs:
         continue-on-error: ${{ matrix.allow_fail }}
 
       - name: Check for vulnerabilities
+        if: ${{ contains(matrix.composer_update_flags, '--prefer-lowest') == false }}
         run: composer security-checker
         continue-on-error: ${{ matrix.allow_fail }}