(DOCSP-44273) Adds MDB 6.0 deprecation to RNs. (#464)

- [DOCSP-44273](https://jira.mongodb.org/browse/DOCSP-44273)
-
[STAGING](https://deploy-preview-464--10gen-docs-ops-manager.netlify.app/release-notes/application/#onprem-server-8.0)

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Author: erabil-mdb

source/release-notes/changelogs/ops-manager/changelog-onprem-v8.0.rst

@@ -28,6 +28,7 @@ MongoDB Cluster Management
      are not supported when you use config shards.
 
 - Deprecates support for MongoDB 4.4 and MongoDB 5.0 deployments.
+- Deprecates support for MongoDB Server 6.0 as a :ref:`backing database <om-install-backing-dbs>`.
 - Removes support for MongoDB 4.2 deployments.
 
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