Hide the "Clear cache" dropdown in the dependency proxy page for auditors

Summary

Identified after completing !88096 (merged)

Auditor users are able to see the Clear cache dropdown in a project's Dependency Proxy page. If an auditor attempts to clear the cache, it returns a 403 code which is expected.

In terms of UX, we should hide the Clear cache dropdown.

Steps to reproduce

From GitLab 15.1:

1. As an auditor user, access a project's Dependency Proxy page.
2. You should see the Clear cache dropdown on the right side.

Example Project

N/A

What is the current bug behavior?

The Clear Cache dropdown is displayed for auditor users when viewing a project's Dependency Proxy page.

What is the expected correct behavior?

The Clear Cache dropdown should be hidden for auditor users when viewing a project's Dependency Proxy page.

Relevant logs and/or screenshots

Output of checks

Results of GitLab environment info

Expand for output related to GitLab environment info

(For installations with omnibus-gitlab package run and paste the output of:
`sudo gitlab-rake gitlab:env:info`)

(For installations from source run and paste the output of:
`sudo -u git -H bundle exec rake gitlab:env:info RAILS_ENV=production`)

Results of GitLab application Check

Expand for output related to the GitLab application check

(For installations with omnibus-gitlab package run and paste the output of:
sudo gitlab-rake gitlab:check SANITIZE=true)
(For installations from source run and paste the output of:
sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production SANITIZE=true)
(we will only investigate if the tests are passing)

Possible fixes

Visibility is controlled by the showDeleteDropdown function in https://gitlab.com/gitlab-org/gitlab/-/blob/v14.10.2-ee/app/assets/javascripts/packages_and_registries/dependency_proxy/app.vue#L184-200