Only render position field on table when cards rendered are not headers

spec/system/admin/widgets/cards_spec.rb

@@ -142,6 +142,7 @@ describe "Cards", :admin do
 
       within("#header") do
         expect(page).to have_css(".homepage-card", count: 1)
+        expect(page).not_to have_css "th", exact_text: "Position"
         expect(page).to have_content "Header label"
         expect(page).to have_content "Header text"
         expect(page).to have_content "Header description"

spec/system/sdg_management/homepage_spec.rb

@@ -70,6 +70,7 @@ describe "SDG homepage configuration" do
       within(".sdg-header") do
         expect(page).to have_content "My header"
         expect(page).not_to have_content "Create header"
+        expect(page).not_to have_css "th", exact_text: "Position"
       end
     end