Updated asset path in favicon_spec.rb to match CE

spec/lib/gitlab/favicon_spec.rb

@@ -9,7 +9,7 @@ RSpec.describe Gitlab::Favicon, :request_store do
 
     it 'has blue favicon for development', unless: Gitlab.ee? do
       allow(Rails).to receive(:env).and_return(ActiveSupport::StringInquirer.new('development'))
-      expect(described_class.main).to match_asset_path 'favicon-blue.png'
+      expect(described_class.main).to match_asset_path '/assets/favicon-blue.png'
     end
 
     it 'has yellow favicon for canary' do