Fix CHANGELOG by moving 8.5.5 items to 8.6

[ci skip]

CHANGELOG

@@ -14,6 +14,7 @@ v 8.6.0 (unreleased)
   - Add support for wiki with UTF-8 page names (Hiroyuki Sato)
   - Fix wiki search results point to raw source (Hiroyuki Sato)
   - Don't load all of GitLab in mail_room
+  - HTTP error pages work independently from location and config (Artem Sidorenko)
   - Update `omniauth-saml` to 1.5.0 to allow for custom response attributes to be set
   - Memoize @group in Admin::GroupsController (Yatish Mehta)
   - Indicate how much an MR diverged from the target branch (Pierre de La Morinerie)
@@ -41,6 +42,7 @@ v 8.6.0 (unreleased)
   - Add shortcut to toggle markdown preview (Florent Baldino)
   - Show labels in dashboard and group milestone views
   - Add main language of a project in the list of projects (Tiago Botelho)
+  - Add #upcoming filter to Milestone filter (Tiago Botelho)
   - Add ability to show archived projects on dashboard, explore and group pages
   - Move group activity to separate page
   - Create external users which are excluded of internal and private projects unless access was explicitly granted
@@ -62,8 +64,6 @@ v 8.5.5
   - Prevent a 500 error in Todos when author was removed
   - Fix pagination for filtered dashboard and explore pages
   - Fix "Show all" link behavior
-  - Add #upcoming filter to Milestone filter (Tiago Botelho)
-  - HTTP error pages work independently from location and config (Artem Sidorenko)
 
 v 8.5.4
   - Do not cache requests for badges (including builds badge)