feat: scale the scheme details page by 2/3 to match the locations list page

app/views/schemes/show.html.erb

@@ -10,6 +10,8 @@
 
 <%= render partial: "organisations/headings", locals: { main: @scheme.service_name, sub: nil } %>
 
+<div class="govuk-grid-row">
+  <div class="govuk-grid-column-two-thirds-from-desktop"> 
     <%= render SubNavigationComponent.new(items: scheme_items(request.path, @scheme.id, "Locations")) %>
 
     <h2 class="govuk-visually-hidden">Scheme</h2>
@@ -25,6 +27,9 @@
       <% end %>
     <% end %>
 
+  </div>
+</div>
+
 <% if FeatureToggle.scheme_toggle_enabled? %>
   <% if @scheme.active? || @scheme.reactivating_soon? %>
     <%= govuk_button_link_to "Deactivate this scheme", scheme_new_deactivation_path(@scheme), warning: true %>