Replace deprecated to: for action: at routes

Running test suite the following appears: DEPRECATION WARNING: Defining
a route where `to` is a symbol is deprecated. Please change
`to: :json_data` to `action: :json_data`.

config/routes/budget.rb

@@ -18,4 +18,4 @@ scope '/participatory_budget' do
   end
 end
 
-get 'investments/:id/json_data', to: :json_data, controller: 'budgets/investments'
+get 'investments/:id/json_data', action: :json_data, controller: 'budgets/investments'