Don't loop over budget phases in system tests

We've already got model tests for that, and we were modifying the
database after a `visit`, since we were doing a loop consisting of
"update!" -> "visit" -> "update!" -> "visit!" -> (...).

Besides, note that the `.kind_or_later("publishing_prices").each` block
wasn't modifying the budget, so it always visited the page under the
same conditions.

So we're simply randomly checking one phase to test that the user
interface works as expected.

spec/system/budgets/investments_spec.rb

@@ -529,10 +529,16 @@ describe "Budget Investments" do
     end
 
     scenario "Order always is random for unfeasible and unselected investments" do
-      Budget::Phase::kind_or_later("valuating").each do |phase|
+      phase = Budget::Phase::kind_or_later("valuating").sample
       budget.update!(phase: phase)
 
-        visit budget_investments_path(budget, heading_id: heading.id, filter: "unfeasible")
+      filter = if Budget::Phase.kind_or_later("publishing_prices").include?(phase)
+                 "unselected"
+               else
+                 "unfeasible"
+               end
+
+      visit budget_investments_path(budget, heading_id: heading.id, filter: filter)
 
       within(".submenu") do
         expect(page).to have_content "random"
@@ -541,17 +547,6 @@ describe "Budget Investments" do
       end
     end
 
-      Budget::Phase.kind_or_later("publishing_prices").each do |phase|
-        visit budget_investments_path(budget, heading_id: heading.id, filter: "unselected")
-
-        within(".submenu") do
-          expect(page).to have_content "random"
-          expect(page).not_to have_content "price"
-          expect(page).not_to have_content "highest rated"
-        end
-      end
-    end
-
     def investments_order
       all(".budget-investment h3").map(&:text)
     end
@@ -872,7 +867,7 @@ describe "Budget Investments" do
 
     context "When investment with price is selected" do
       scenario "Price & explanation is shown when Budget is on published prices phase" do
-        Budget::Phase::PUBLISHED_PRICES_PHASES.each do |phase|
+        phase = Budget::Phase::PUBLISHED_PRICES_PHASES.sample
         budget.update!(phase: phase)
 
         if budget.finished?
@@ -889,10 +884,9 @@ describe "Budget Investments" do
 
         expect(page).to have_content(investment.formatted_price)
       end
-      end
 
       scenario "Price & explanation isn't shown when Budget is not on published prices phase" do
-        (Budget::Phase::PHASE_KINDS - Budget::Phase::PUBLISHED_PRICES_PHASES).each do |phase|
+        phase = (Budget::Phase::PHASE_KINDS - Budget::Phase::PUBLISHED_PRICES_PHASES).sample
         budget.update!(phase: phase)
         visit budget_investment_path(budget, id: investment.id)
 
@@ -905,7 +899,6 @@ describe "Budget Investments" do
         expect(page).not_to have_content(investment.formatted_price)
       end
     end
-    end
 
     context "When investment with price is unselected" do
       before do
@@ -913,7 +906,7 @@ describe "Budget Investments" do
       end
 
       scenario "Price & explanation isn't shown for any Budget's phase" do
-        Budget::Phase::PHASE_KINDS.each do |phase|
+        phase = Budget::Phase::PHASE_KINDS.sample
         budget.update!(phase: phase)
         visit budget_investment_path(budget, id: investment.id)
 
@@ -927,7 +920,6 @@ describe "Budget Investments" do
       end
     end
   end
-  end
 
   scenario "Can access the community" do
     Setting["feature.community"] = true