add AMI update step

doc/release/monthly.md

@@ -200,3 +200,7 @@ Consider creating a post on Hacker News.
 ## Update GitLab.com with the stable version
 
 - Deploy the package (should not need downtime because of the small difference with RC1)
+
+## Release new AMIs
+
+[Follow this guide](https://dev.gitlab.org/gitlab/AMI/blob/master/README.md)

doc/release/patch.md

@@ -54,3 +54,4 @@ CE=false be rake release['x.x.x']
 1. Create and publish a blog post, see [patch release blog template](https://gitlab.com/gitlab-com/www-gitlab-com/blob/master/doc/patch_release_blog_template.md)
 1. Send tweets about the release from `@gitlab`, tweet should include the most important feature that the release is addressing and link to the blog post
 1. Note in the 'GitLab X.X regressions' issue that the patch was published (CE only)
+1. [Create new AMIs](https://dev.gitlab.org/gitlab/AMI/blob/master/README.md)