Use #url helper

app/views/spree/admin/images/edit.html.haml

@@ -11,9 +11,7 @@
     .field.alpha.three.columns.align-center
       = f.label t('spree.thumbnail')
       %br/
-      - # A Rails bug makes it necessary to call `main_app.url_for` here.
-      - # https://github.com/rails/rails/issues/31325
-      = link_to image_tag(main_app.url_for(@image.variant(:small))), main_app.url_for(@image.variant(:product))
+      = link_to image_tag(@image.url(:small)), @image.url(:product)
     .nine.columns.omega
       = render partial: 'form', locals: { f: f }
     .clear

app/views/spree/admin/images/index.html.haml

@@ -32,9 +32,7 @@
           %td.no-border
             %span.handle
           %td
-            - # A Rails bug makes it necessary to call `main_app.url_for` here.
-            - # https://github.com/rails/rails/issues/31325
-            = link_to image_tag(main_app.url_for(image.variant(:mini))), main_app.url_for(image.variant(:product))
+            = link_to image_tag(image.url(:mini)), image.url(:product)
           %td= options_text_for(image)
           %td= image.alt
           %td.actions