Remove outdated changelog file

This hasn't been updated in 2 years and we have CHANGELOG.md now.

CHANGELOG

-## 2017-02-20
-
-- Overall CSS styling fixes
-- Current theme is displayed in theme selector
-- Theme selector is moved to the settings page
-- Oembed attachments will now display correctly
-- Styling changes to the user info cards
-- Notification count in title
-- Better Notification handling (persistance, mark as read)
-- Post statuses with ctrl+enter
-- Links in statuses open in a new tab
-- Optimized mobile view
-- Fix crash on persistance failure
-- Compress persisted state
-- Sync mutes with backend (SEE NOTE BELOW)
-
-Pleroma will now try to get the current mutes from the backend. Sadly, a bug in
-Qvitter will not allow getting the mutes from the endpoint, because it will
-ignore HTTP Basic authentication. Mutes will still persist in Pleroma through
-localstorage, but the mutes from Qvitter won't be picked up if the call fails.
-
-The patch for Qvitter:
-
---- a/actions/apiqvittermutes.php
-+++ b/actions/apiqvittermutes.php
-@@ -74,7 +74,7 @@ class ApiQvitterMutesAction extends ApiPrivateAuthAction
-     {
-         parent::handle();
-
--        $this->target = Profile::current();
-+        $this->target = $this->scoped;
-
-                if(!$this->target instanceof Profile) {
-                        $this->clientError(_('You have to be logged in to view your mutes.'), 403);
-