remove asterisk on 'display as' field unit value for a product

as it's not a mandatory field

app/views/spree/admin/products/_display_as.html.haml

@@ -1,5 +1,4 @@
 .three.columns.omega{ "ng-if" => "product.variant_unit_with_scale != 'items'" }
   = f.field_container :display_as do
     = f.label :product_display_as, t('.display_as')
-    %span.required *
     %input#product_display_as.fullwidth{name: "product[display_as]", placeholder: "{{ placeholder_text }}", type: "text"}