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/budgets/investments_spec.rb

@@ -1169,6 +1169,7 @@ describe "Budget Investments" do
 
       refresh
 
+      expect(page).not_to have_content "Investment project deleted successfully"
       expect(page).to have_content "User has no public activity"
       expect(page).not_to have_content investment1.title
     end