fix: improve PostgreSQL healthcheck cmd to avoid fatal log errors (#22749) (#22917)

docker/docker-compose.middleware.yaml

     ports:
       - "${EXPOSE_POSTGRES_PORT:-5432}:5432"
     healthcheck:
-      test: [ "CMD", "pg_isready" ]
+      test: [ 'CMD', 'pg_isready', '-h', 'db', '-U', '${PGUSER:-postgres}', '-d', '${POSTGRES_DB:-dify}' ]
       interval: 1s
       timeout: 3s
       retries: 30