Gramps: reduce celery workers to 1

And update valkey to 9

files/gramps/docker-compose.template.yml

@@ -53,10 +53,10 @@ services:
     ports: []
     networks:
       - "gramps_network"
-    command: celery -A gramps_webapi.celery worker --loglevel=INFO --concurrency=2
+    command: celery -A gramps_webapi.celery worker --loglevel=INFO --concurrency=1
 
   gramps_redis:
-    image: valkey/valkey:8.1.1-alpine
+    image: valkey/valkey:9-alpine
     container_name: gramps_redis
     restart: unless-stopped
     networks: