Merge branch 'deprecated-instance-find' into 'master'

Fix deprecation: You are passing an instance of ActiveRecord::Base to find

See merge request gitlab-org/gitlab-ce!23369

changelogs/unreleased/deprecated-instance-find.yml

+---
+title: 'Fix deprecation: You are passing an instance of ActiveRecord::Base to'
+merge_request: 23369
+author: Jasper Maes
+type: other

spec/workers/rebase_worker_spec.rb

@@ -19,7 +19,7 @@ describe RebaseWorker, '#perform' do
       expect(MergeRequests::RebaseService)
         .to receive(:new).with(forked_project, merge_request.author).and_call_original
 
-      subject.perform(merge_request, merge_request.author)
+      subject.perform(merge_request.id, merge_request.author.id)
     end
   end
 end