Update docs/changelog/126623.yaml

Author: not-napoleon

docs/changelog/126623.yaml

@@ -1,7 +1,14 @@
 pr: 126623
 summary: Enable synthetic source on normalized keyword mappings
 area: Mapping
-type: enhancement
+type: "breaking, enhancement"
 issues:
  - 124369
  - 121358
+breaking:
+  title: Enable synthetic source on normalized keyword mappings
+  area: Mapping
+  details: Please describe the details of this change for the release notes. You can
+    use asciidoc.
+  impact: Please describe the impact of this change to users
+  notable: false