Remove redundant database checks in system tests

These tests check what happens from the user's point of view. For
instance, we check that after disabling recommendations, they are not
shown. What happens in the database is not related to the user
experience.

Furthermore, checking the database after the browser has started is
proving to be a major source for inconsistent data in specs.

spec/system/admin/hidden_users_spec.rb

@@ -37,8 +37,6 @@ describe "Admin hidden users", :admin do
     expect(page).not_to have_content(user.username)
     click_link("Confirmed")
     expect(page).to have_content(user.username)
-
-    expect(user.reload).to be_confirmed_hide
   end
 
   scenario "Current filter is properly highlighted" do