Simplify owner selection in spec

Instead of knowing the input id generated by select2, we now rely on the
fact that the owner is in the fifth column. Both could change but this
is less code.

spec/system/admin/enterprises/index_spec.rb

@@ -87,12 +87,9 @@ describe 'Enterprises Index' do
         end
 
         def select_new_owner(user, enterprise)
-          enterprise_row_number = all('tr').index { |tr| tr.text.include? enterprise.name }
-          enterprise_row_number -= 1
-
-          within("tr.enterprise-#{enterprise.id}") do
-            select user.email,
-                   from: "sets_enterprise_set_collection_attributes_#{enterprise_row_number}_owner_id"
+          # The fifth table column contains the owner field.
+          within("tr.enterprise-#{enterprise.id} td:nth-child(5)") do
+            select user.email
           end
         end
       end