Merge branch 'docs-add-s3-response-warning' into 'master'

Add S3 warning to Package Docs

See merge request gitlab-org/gitlab!24729

doc/administration/packages/index.md

@@ -118,7 +118,10 @@ upload packages:
      #'path_style' => false                    # If true, use 'host/bucket_name/object' instead of 'bucket_name.host/object'.
    }
    ```
-
+  
+   NOTE: **Note:**
+   Some build tools, like Gradle, must make `HEAD` requests to Amazon S3 to pull a dependency’s metadata. The `gitlab_rails['packages_object_store_proxy_download']` property must be set to `true`. Without this setting, GitLab won't act as a proxy to the Amazon S3 service, and will instead return the signed URL. This will cause a `HTTP 403 Forbidden` response, since Amazon S3 expects a signed URL.
+  
 1. Save the file and [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure)
    for the changes to take effect.