add note about max_instances in local dev docs

Author: dario-piotrowicz

src/content/docs/containers/local-dev.mdx

@@ -30,6 +30,9 @@ If your Worker app creates many container instances, your local machine may not
 
 Additionally, if you regularly rebuild containers locally, you may want to clear
 out old container images (using `docker image prune` or similar) to reduce disk used.
+
+Also note that the `max_instances` configuration option is only enforced when running in production on Cloudflare's network.
+During local development the limit is not applied, so you may run more instances than specified.
 :::
 
 ## Iterating on Container code