DOCS-15967 internal server data cleanup must complete before upgrade (#4205)

* DOCS-15967 internal server data cleanup must complete before upgrade

* DOCS-15967 updates for feedback

* Update source/reference/command/setFeatureCompatibilityVersion.txt

Co-authored-by: Sarah Olson <[email protected]>

* Update source/reference/command/setFeatureCompatibilityVersion.txt

Co-authored-by: Sarah Olson <[email protected]>

* DOCS-15967 updates for feedback

---------

Co-authored-by: Sarah Olson <[email protected]>

Author: kanchana-mongodb

source/reference/command/setFeatureCompatibilityVersion.txt

@@ -162,6 +162,11 @@ To move the cluster out of the ``downgrading`` state, either:
      This procedure does not reset the cluster back to the state before
      the {+fcv+} downgrade began.
 
+     If a failed {+fcv+} downgrade's internal metadata is not
+     cleaned up, any subsequent FCV upgrade attempt fails with an
+     error message. You must complete the {+fcv+} downgrade before
+     trying to upgrade the {+fcv+}.
+
 Downgrade Policy Changes in MongoDB 7.0
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~