Update CHANGELOG-EE.md for 12.9.8-ee

[ci skip]

CHANGELOG-EE.md

@@ -418,6 +418,15 @@ Please view this file on the master branch, on stable branches it's out of date.
 - Add health status counts to usage data. !28964
 
 
+## 12.9.8 (2020-05-27)
+
+### Security (3 changes)
+
+- Change the mirror user along with pull mirror settings.
+- Allow only users with a verified email to be member of a group when the group has restricted membership based on email domain.
+- Do not auto-confirm email in Trial registration.
+
+
 ## 12.9.6 (2020-05-05)
 
 - No changes.