Remove duplicate external URL

The external URL is already rendered in the `investment_detail` partial,
so we were rendering it twice in the valuation area.

app/views/valuation/budget_investments/show.html.erb

@@ -19,10 +19,6 @@
 <%= render "/budgets/investments/investment_detail", investment: @investment, preview: true %>
 </hr>
 
-<% if @investment.external_url.present? %>
-  <p><%= sanitize_and_auto_link @investment.external_url %></p>
-<% end %>
-
 <hr>
 
 <h2><%= t("valuation.budget_investments.show.responsibles") %></h2>