Improve spinach test to be more specific about link to click

If you add another branch to gitlab-test that includes the word 'test',
browse_files.feature will fail with an ambiguous match.

features/steps/project/source/browse_files.rb

@@ -293,7 +293,7 @@ class Spinach::Features::ProjectSourceBrowseFiles < Spinach::FeatureSteps
     first('.js-project-refs-dropdown').click
 
     page.within '.project-refs-form' do
-      click_link 'test'
+      click_link "'test'"
     end
   end