Add budget investment factory to fix failing scenario

Changes introduced in commits 41f66fa and dc87b75 will render the
'See results' button under `admin/budget_investments` only if a
finished budget has winner investments associated with it

spec/features/admin/budget_investments_spec.rb

@@ -541,21 +541,18 @@ feature 'Admin budget investments' do
     end
 
     scenario "See results button appears when budget status is finished" do
-
       finished_budget = create(:budget, :finished)
+      create(:budget_investment, :winner, budget: finished_budget, title: "Winner project")
 
       visit admin_budget_budget_investments_path(budget_id: finished_budget.id)
       expect(page).to have_content "See results"
-
     end
 
     scenario "See results button does not appear for unfinished budgets" do
-
       not_finished_budget = create(:budget, :valuating)
 
       visit admin_budget_budget_investments_path(budget_id: not_finished_budget.id)
       expect(page).not_to have_content "See results"
-
     end
 
   end