Update 8.13.0.asciidoc (#106803)

* Update 8.13.0.asciidoc

Introduce notable changes in place of breaking changes.

* Update copy, heading format

* Update

---------

Co-authored-by: Liam Thompson <[email protected]>

Author: dbrimley

docs/reference/release-notes/8.13.0.asciidoc

@@ -6,6 +6,17 @@ Also see <<breaking-changes-8.13,Breaking changes in 8.13>>.
 [[breaking-8.13.0]]
 [float]
 === Breaking changes
+There are no breaking changes in 8.13.0.
+
+[[notable-changes-8.13.0]]
+[float]
+=== Notable changes
+The following are notable, non-breaking updates to be aware of:
+
+* Changes to features that are in Technical Preview.
+* Changes to log formats.
+* Changes to non-public APIs.
+* Behaviour changes that repair critical bugs.
 
 ES|QL::
 * ESQL: Grammar - FROM METADATA no longer requires [] {es-pull}105221[#105221]