Check table rows content instead of database

Checking the database with methods like Activity.last does not test that
the record is present where it should be (first record of the table in
this case). In these tests there's only one record, though, so the order
doesn't matter that match.

However, calling methods like Activity.last generates a database query
after the process running the browser has been started, and this might
lead to inconsistent data.

spec/system/officing/results_spec.rb

@@ -73,7 +73,7 @@ describe "Officing Results", :with_frozen_time do
 
     expect(page).to have_content("Your results")
 
-    within("#results_#{poll_officer.officer_assignments.first.booth_assignment_id}_#{Date.current.strftime("%Y%m%d")}") do
+    within "tbody tr" do
       expect(page).to have_content(I18n.l(Date.current, format: :long))
       expect(page).to have_content(booth.name)
     end