Add the shared file content (#168) (#169)

(cherry picked from commit aca2f0f)

Co-authored-by: Clayton Cornell <[email protected]>

docs/sources/shared/agent-deprecation.md

@@ -0,0 +1,21 @@
+---
+headless: true
+labels:
+  products:
+    - enterprise
+    - oss
+---
+
+[//]: # 'This file provides an admonition caution to change to Grafana Agent to Grafana Alloy.'
+[//]: # 'This shared file is included in many repositories.'
+[//]: #
+[//]: # 'If you make changes to this file, verify that the meaning and content are not changed in any place where the file is included.'
+[//]: # 'Any links should be fully qualified and not relative: /docs/grafana/ instead of ../grafana/.'
+
+{{< admonition type="caution" >}}
+Grafana Alloy is the new name for our distribution of the OTel collector.
+Grafana Agent has been deprecated and is in Long-Term Support (LTS) through October 31, 2025. Grafana Agent will reach an End-of-Life (EOL) on November 1, 2025.
+Read more about why we recommend migrating to [Grafana Alloy][alloy].
+
+[alloy]: https://grafana.com/blog/2024/04/09/grafana-alloy-opentelemetry-collector-with-prometheus-pipelines/
+{{< /admonition >}}