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/proposals_spec.rb

@@ -80,7 +80,6 @@ describe "Admin proposals", :admin do
 
       expect(page).to have_content "Proposal updated successfully"
       expect(find_field("Mark as selected")).to be_checked
-      expect(proposal.reload.selected?).to be true
     end
 
     scenario "Unselect a proposal" do
@@ -93,7 +92,6 @@ describe "Admin proposals", :admin do
 
       expect(page).to have_content "Proposal updated successfully"
       expect(find_field("Mark as selected")).not_to be_checked
-      expect(proposal.reload.selected?).to be false
     end
   end
 end