[DOCS] Add 6.8.14 ml-cpp PRs to release notes (#68682)

Author: lcawl

docs/reference/release-notes.asciidoc

@@ -5,6 +5,7 @@
 --
 This section summarizes the changes in each release.
 
+* <<release-notes-6.8.14>>
 * <<release-notes-6.8.13>>
 * <<release-notes-6.8.12>>
 * <<release-notes-6.8.11>>

docs/reference/release-notes/6.8.asciidoc

@@ -1,3 +1,19 @@
+[[release-notes-6.8.14]]
+== {es} version 6.8.14
+
+coming::[6.8.14]
+
+Also see <<breaking-changes-6.8,Breaking changes in 6.8>>.
+
+[[bug-6.8.14]]
+[float]
+=== Bug fixes
+
+Machine learning::
+* Fixes missing state in persist and restore for anomaly detection. This caused
+suboptimal modeling after a job was closed and reopened or failed over to a
+different node {ml-pull}1668[#1668]
+
 
 [[release-notes-6.8.13]]
 == {es} version 6.8.13