Add and apply Lint/DuplicateBranch rubocop rule

This rule was introduced in rubocop 1.3.0.

.rubocop.yml

@@ -160,6 +160,9 @@ Lint/BooleanSymbol:
 Lint/ConstantDefinitionInBlock:
   Enabled: true
 
+Lint/DuplicateBranch:
+  Enabled: true
+
 Lint/DuplicateMethods:
   Enabled: true
 

app/models/budget.rb

@@ -187,12 +187,10 @@ class Budget < ApplicationRecord
 
   def investments_orders
     case phase
-    when "accepting", "reviewing"
+    when "accepting", "reviewing", "finished"
       %w[random]
     when "publishing_prices", "balloting", "reviewing_ballots"
       %w[random price]
-    when "finished"
-      %w[random]
     else
       %w[random confidence_score]
     end