DOCSP-23184 adds links to upgrade procedures (#1221)

* adds links to upgrade procedures

* internal review updates

Author: jmd-mongo

source/release-notes/6.0.txt

@@ -668,6 +668,30 @@ a detailed list of compatibility changes, see
 Upgrade Procedures
 ------------------
 
+.. important:: Feature Compatibility Version
+
+   To upgrade to MongoDB 6.0 from a 5.0 deployment, the 5.0 deployment
+   must have ``featureCompatibilityVersion`` set to ``5.0``. To check
+   the version:
+
+   .. code-block:: javascript
+
+      db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )
+
+To upgrade to MongoDB 6.0, refer to the upgrade instructions specific to
+your MongoDB deployment:
+
+- :ref:`<6.0-upgrade-standalone>`
+
+- :ref:`<6.0-upgrade-replica-set>`
+
+- :ref:`<6.0-upgrade-sharded-cluster>`
+
+If you need guidance on upgrading to 6.0, MongoDB professional services
+offer major version upgrade support to help ensure a smooth transition
+without interruption to your MongoDB application. To learn more, see
+:products:`MongoDB Consulting </consulting?tck=docs_server>`.
+
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