Add Predis adapter to blackbox tests in GitHub Actions workflow

Signed-off-by: Lukas Kämmerling <lukas.kaemmerling@hetzner-cloud.de>

Author: LKaemmerling

.github/workflows/blackbox.yml

@@ -40,6 +40,8 @@ jobs:
         run: docker compose run phpunit env ADAPTER=apcng vendor/bin/phpunit tests/Test/
       - name: Run Blackbox with Redis
         run: docker compose run phpunit env ADAPTER=redis vendor/bin/phpunit tests/Test/
+      - name: Run Blackbox with Predis
+        run: docker compose run phpunit env ADAPTER=predis vendor/bin/phpunit tests/Test/