Added Rake:Attack cp information to Upgrade Guide 6.3.0

doc/update/6.2-to-6.3.md

@@ -63,7 +63,12 @@ git diff 6-2-stable:config/gitlab.yml.example 6-3-stable:config/gitlab.yml.examp
 * Make `/home/git/gitlab/config/gitlab.yml` same as https://github.com/gitlabhq/gitlabhq/blob/6-3-stable/config/gitlab.yml.example but with your settings.
 * Make `/home/git/gitlab/config/unicorn.rb` same as https://github.com/gitlabhq/gitlabhq/blob/6-3-stable/config/unicorn.rb.example but with your settings.
-* Copy rack attack middleware config
+
+```bash
+# Copy rack attack middleware config
+cd /home/git/gitlab
+sudo -u git -H cp config/initializers/rack_attack.rb.example config/initializers/rack_attack.rb
+```
 ### 6. Update Init script