Merge branch 'rails5-nil-formats' into 'master'

Fix nil formats test

Closes #47833

See merge request gitlab-org/gitlab-ce!19941

spec/lib/gitlab/auth/user_auth_finders_spec.rb

@@ -99,7 +99,7 @@ describe Gitlab::Auth::UserAuthFinders do
 
     context 'when the request format is empty' do
       it 'the method call does not modify the original value' do
-        env['action_dispatch.request.formats'] = nil
+        env.delete('action_dispatch.request.formats')
 
         find_user_from_feed_token