feat: simplify "scheme_id: @scheme.id" to "@scheme"

app/views/locations/index.html.erb

@@ -49,7 +49,7 @@
           <% end %>
         <% end %>
       <% end %>
-      <%= govuk_button_link_to "Add a location", new_scheme_location_path(scheme_id: @scheme.id), secondary: true %>
+      <%= govuk_button_link_to "Add a location", new_scheme_location_path(@scheme), secondary: true %>
     </div>
   </div>
 
@@ -105,7 +105,7 @@
       <% end %>
     <% end %>
   <% end %>
-  <%= govuk_button_link_to "Add a location", new_scheme_location_path(scheme_id: @scheme.id), secondary: true %>
+  <%= govuk_button_link_to "Add a location", new_scheme_location_path(@scheme), secondary: true %>
 
 <% end %>