Add link to GitLab Changelog With Version Check

The version check currently makes a request to
https://version.gitlab.com that returns an SVG reporting to the user
whether or not the instance is up-to-date, with no feedback on what has
changed.

We can at least add a link to the changelog for the GitLab project, so
it is easier to view the reason for changes.

Changelog: changed

app/views/admin/dashboard/index.html.haml

@@ -118,6 +118,7 @@
             - if Gitlab::CurrentSettings.version_check_enabled
               .float-right
                 = version_status_badge
+                = link_to(sprite_icon('question'), "https://gitlab.com/gitlab-org/gitlab/-/blob/master/CHANGELOG.md", class: 'gl-ml-2', target: '_blank', rel: 'noopener noreferrer')
           %p
             = link_to _('GitLab'), general_admin_application_settings_path
             %span.float-right

spec/views/admin/dashboard/index.html.haml_spec.rb

@@ -52,4 +52,12 @@ RSpec.describe 'admin/dashboard/index.html.haml' do
     expect(rendered).not_to have_content "Maximum Users"
     expect(rendered).not_to have_content "Users over License"
   end
+
+  it 'links to the GitLab Changelog' do
+    stub_application_setting(version_check_enabled: true)
+
+    render
+
+    expect(rendered).to have_link(href: 'https://gitlab.com/gitlab-org/gitlab/-/blob/master/CHANGELOG.md')
+  end
 end