Fix a wrong URL in 'SystemNotes::MergeRequestsService' spec

Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/services/system_notes/merge_requests_service_spec.rb

@@ -253,7 +253,7 @@ describe ::SystemNotes::MergeRequestsService do
     end
 
     it "posts the 'picked merge request' system note" do
-      expect(subject.note).to eq("picked this merge request into branch [`#{branch_name}`](/#{project.full_path}/tree/#{branch_name}) with commit #{commit_sha}")
+      expect(subject.note).to eq("picked this merge request into branch [`#{branch_name}`](/#{project.full_path}/-/tree/#{branch_name}) with commit #{commit_sha}")
     end
 
     it 'links the merge request and the cherry-pick commit' do