Add to_param to mentionable spec's mock

spec/support/mentionable_shared_examples.rb

@@ -53,7 +53,7 @@ def common_mentionable_setup
     extra_commits.each { |c| commitmap[c.short_id] = c }
 
     allow(project.repository).to receive(:commit) { |sha| commitmap[sha] }
-    
+
     set_mentionable_text.call(ref_string)
   end
 end