Move "GItLab Pages" CHANGELOG entry to EE

[ci skip]

CHANGELOG

@@ -20,7 +20,6 @@ v 8.3.0 (unreleased)
   - Trim leading and trailing whitespace of milestone and issueable titles (Jose Corcuera)
   - Recognize issue/MR/snippet/commit links as references
   - Add ignore whitespace change option to commit view
-  - Add GitLab Pages
   - Fire update hook from GitLab
   - Style warning about mentioning many people in a comment
   - Fix: sort milestones by due date once again (Greg Smethells)

CHANGELOG-EE

@@ -3,6 +3,7 @@ v 8.3.0 (unreleased)
   - Show Kerberos clone url when Kerberos enabled and url different than HTTP url (Borja Aparicio)
   - Fix bug with negative approvals required
   - Add group contribution statistics page 
+  - Add GitLab Pages
 
 v 8.2.3
   - No EE-specific changes