Merge branch 'atevans-dependency-proxy-registry-note' into 'main'

Add note to dependency proxy docs that registry should also be enabled

See merge request https://gitlab.com/gitlab-org/gitlab-development-kit/-/merge_requests/3652



Merged-by: Evan Read <eread@gitlab.com>
Approved-by: Evan Read <eread@gitlab.com>
Co-authored-by: Andrew Evans <aevans@gitlab.com>

doc/howto/dependency_proxy.md

 # Dependency Proxy
 
 This document describes how to enable the [dependency proxy](https://docs.gitlab.com/ee/user/packages/dependency_proxy/)
-in your GDK environment.
+in your GDK environment. 
+
+Some dependency proxy operations require token scopes that are only available when the container registry is enabled. You should
+[enable the registry](registry.md#set-up-pushing-and-pulling-of-images-over-http) when developing or testing features related to the dependency proxy.
 
 ## Configuration