Update CHANGELOG.md for 13.9.7-ee

[ci skip]

CHANGELOG.md

@@ -1411,6 +1411,18 @@ entry.
 - Convert mattermost alert to pajamas. !56556
 
 
+## 13.9.7 (2021-04-27)
+
+### Security (6 changes)
+
+- Prevent tokens with only read_api scope from executing mutations.
+- Update mermaid to version 8.9.2.
+- Do not allow deploy tokens in the dependency proxy authentication service.
+- Disable keyset pagination for branches by default.
+- Bump Carrierwave gem to v1.3.2.
+- Restrict setting system_note_timestamp to owners.
+
+
 ## 13.9.6 (2021-04-13)
 
 ### Security (2 changes)