Add missing expectations after refreshing the page

This way we know for sure the page has finished refreshing.

Note that, for now, we aren't adding a check after every call to the
`refresh` method because sometimes the page remains identical after
refreshing. Not sure what we should do in these cases.

spec/system/admin/poll/questions/options/options_spec.rb

@@ -66,6 +66,7 @@ describe "Poll question options", :admin do
 
     refresh
 
+    expect(page).not_to have_content "Changes saved"
     expect(page).not_to have_content "Answer title"
 
     expect("Another title").to appear_before("New title")