Add 9.0.5 CHANGELOG

CHANGELOG.md

@@ -7,6 +7,13 @@ omnibus-gitlab repository.
 - Remove deprecated satellites configuration
+9.0.5
+
+- Build SLES 12 EE package at the same time as others.
+- Fix AWS build errors
+- Updating documentation for external PostgreSQL usage
+- Added quotes to GITLAB_SKIP_PG_UPGRADE
+
 9.0.4
 - Update Mattermost version to 3.7.3 b8abd225