Update status group name for success with warnings

lib/gitlab/ci/status/pipeline/success_with_warnings.rb

@@ -17,7 +17,7 @@ module Gitlab
             'icon_status_warning'
           end
 
-          def to_s
+          def group
             'success_with_warnings'
           end
 

spec/lib/gitlab/ci/status/pipeline/success_with_warnings_spec.rb

@@ -17,6 +17,10 @@ describe Gitlab::Ci::Status::Pipeline::SuccessWithWarnings do
     it { expect(subject.icon).to eq 'icon_status_warning' }
   end
 
+  describe '#group' do
+    it { expect(subject.group).to eq 'success_with_warnings' }
+  end
+
   describe '.matches?' do
     context 'when pipeline is successful' do
       let(:pipeline) do