Enable HTTP pull mirroring test in all envs

The test was changed to require an admin account because of a
permissions setting that meant only admins could configure
mirrors. That setting has been changed on Staging so that admin
access is no longer needed. It was never restricted on Prod.

qa/qa/specs/features/ee/browser_ui/3_create/repository/pull_mirroring_over_http_spec.rb

@@ -2,11 +2,9 @@
 
 module QA
   context 'Create' do
-    # Use Admin credentials as a workaround for a permissions bug
-    # See https://gitlab.com/gitlab-org/gitlab/issues/13769
-    describe 'Pull mirror a repository over HTTP', :requires_admin do
+    describe 'Pull mirror a repository over HTTP' do
       it 'configures and syncs a (pull) mirrored repository with password auth', testcase: 'https://gitlab.com/gitlab-org/quality/testcases/-/issues/520' do
-        Flow::Login.sign_in_as_admin
+        Flow::Login.sign_in
 
         source = Resource::Repository::ProjectPush.fabricate! do |project_push|
           project_push.project_name = 'pull-mirror-source-project'