Update CHANGELOG-EE for 8.12.6 and 8.12.7

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

CHANGELOG-EE.md

@@ -9,6 +9,14 @@ Please view this file on the master branch, on stable branches it's out of date.
   - Decrease maximum time that GitLab waits for a mirror to finish !791 (Borja Aparicio)
   - User groups (that can be assigned as approvers)
 
+## 8.12.7
+
+  - No EE-specific changes
+
+## 8.12.6
+
+  - No EE-specific changes
+
 ## 8.12.5
 
   - No EE-specific changes