fix: docker-compose 수정

Author: JunRain2

docker/docker-compose.prod.yml

@@ -32,6 +32,7 @@ services:
       GOOGLE_CLIENT_ID: ${GOOGLE_CLIENT_ID}
       GOOGLE_CLIENT_SECRET: ${GOOGLE_CLIENT_SECRET}
       ENCODED_FIREBASE_ADMIN_SDK: ${ENCODED_FIREBASE_ADMIN_SDK}
+      SLACK_ERROR_ALERT_TOKEN: ${SLACK_ERROR_ALERT_TOKEN}
     depends_on:
       - mysql
       - redis