env syntax fix in compose file

docker-compose.yml

@@ -9,7 +9,7 @@ services:
     build: .
     restart: unless-stopped
     ports:
-      - "${APP_Port=8080}:80"
+      - "${APP_Port:-8080}:80"
     environment:
       DATABASE_URL: postgresql://flixcooks:flixcooks_prod@postgres:5432/flixcooks
       FLIXCOOKS_ADMIN_KEY: ${FLIXCOOKS_ADMIN_KEY:-change-me-in-production}