Merge branch 'docs-add-glcom-reg-restictions' into 'master'

Add note on registry restrictions on GitLab.com

See merge request gitlab-org/gitlab-ce!15174

doc/user/project/container_registry.md

@@ -27,7 +27,8 @@ to enable it.
 1. First, ask your system administrator to enable GitLab Container Registry
    following the [administration documentation](../../administration/container_registry.md).
    If you are using GitLab.com, this is enabled by default so you can start using
-   the Registry immediately.
+   the Registry immediately. Currently there is a soft (10GB) size restriction for 
+   registry on GitLab.com, as part of the [repository size limit](repository/index.html#repository-size).
 1. Go to your [project's General settings](settings/index.md#sharing-and-permissions)
    and enable the **Container Registry** feature on your project. For new
    projects this might be enabled by default. For existing projects