fix: syntax error in docker compose file (#8)

Author: Quadrubo

docker-compose.yml

@@ -21,7 +21,7 @@ services:
       # Cron
       - CRON_SCHEDULE=${CRON_SCHEDULE:-0 1 * * *}
       # NTFY
-      - NTFY_SERVER=${NTFY_SERVER:https://ntfy.sh}
+      - NTFY_SERVER=${NTFY_SERVER:-https://ntfy.sh}
       - NTFY_TOPIC=${NTFY_TOPIC}
       - NTFY_USERNAME=${NTFY_USERNAME}
       - NTFY_PASSWORD=${NTFY_PASSWORD}