[DOCS] Add a bug fix for 8.13.3 release notes (elastic#182373)

## Summary

This PR adds a bug fix in the 8.13.3 release notes for the fix from
elastic#178321.

(cherry picked from commit 6423fae)

docs/CHANGELOG.asciidoc

@@ -96,6 +96,8 @@ Fleet::
 * Fixes managed agent policy preconfiguration update ({kibana-pull}181624[#181624]).
 * Use lowercase dataset in template names ({kibana-pull}180887[#180887]).
 * Fixes KQL/kuery for getting Fleet Server agent count ({kibana-pull}180650[#180650]).
+Index Management::
+* Fixes `allow_auto_create` field in the Index Template form ({kibana-pull}178321[#178321]).
 Lens & Visualizations::
 * Fixes controls on fields with custom label ({kibana-pull}180615[#180615]).
 Machine Learning::