Deprecate self hosted LangSmith-Observability helm chart (#2976)

## Overview
Chart is being deprecated

## Type of change

**Type:**
Remove outdated content

## Related issues/PRs
Closes INF-1678

## Checklist
<!-- Put an 'x' in all boxes that apply -->
- [X] I have read the [contributing guidelines](README.md)
- [X] I have tested my changes locally using `docs dev`
- [X] All code examples have been tested and work correctly
- [X] I have used **root relative** paths for internal links
- [X] I have updated navigation in `src/docs.json` if needed


## Additional notes
😢

Author: romain-priour-lc

src/langsmith/export-backend.mdx

@@ -39,15 +39,15 @@ You can use a [Prometheus](https://prometheus.io/docs/prometheus/latest/getting_
 
 ## Frontend Nginx
 
-The frontend service exposes its Nginx metrics at the following endpoint: `langsmith-frontend.langsmith.svc.cluster.local:80/nginx_status`. You can either scrape them yourself, or bring up a Prometheus Nginx exporter using the [LangSmith Observability Helm Chart](/langsmith/observability-stack)
+The frontend service exposes its Nginx metrics at the following endpoint: `langsmith-frontend.langsmith.svc.cluster.local:80/nginx_status`. You can either scrape them yourself, or bring up a [Prometheus Nginx exporter](https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-nginx-exporter).
 
 <Warning>
 **The following sections apply for in-cluster databases only. If you are using external databases, you will need to configure exposing and fetching metrics.**
 </Warning>
 
 ## Postgres + Redis
 
-If you are using in-cluster Postgres/Redis instances, you can use a Prometheus exporter to expose metrics from your instance. You can deploy your own, or if you would like, you can use the [LangSmith Observability Helm Chart](/langsmith/observability-stack) to deploy an exporter for you.
+If you are using in-cluster Postgres/Redis instances, you can use a Prometheus exporter to expose metrics from your instance. You can deploy a [Postgres exporter](https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-postgres-exporter) and/or [Redis exporter](https://github.com/prometheus-community/helm-charts/tree/main/charts/prometheus-redis-exporter).
 
 ## Clickhouse
 

src/langsmith/observability-stack.mdx

@@ -3,6 +3,10 @@ title: Deploy an observability stack for your LangSmith deployment
 sidebarTitle: Deploy an observability stack
 ---
 
+<Danger>
+**Deprecated**: The LangSmith Observability Helm chart is deprecated. We no longer maintain or provide support for it. The documentation below is preserved for reference only.
+</Danger>
+
 <Warning>
 **This section is only applicable for Kubernetes deployments.**
 </Warning>