Revert "FIX: constant lookup error when exporting theme"

This reverts commit 1eda8c50f0.

app/controllers/admin/themes_controller.rb

@@ -190,7 +190,7 @@ class Admin::ThemesController < Admin::AdminController
 
         response.headers['Content-Disposition'] = "attachment; filename=#{@theme.name.parameterize}.dcstyle.json"
         response.sending_file = true
-        render json: ::ThemeWithEmbeddedUploadsSerializer.new(@theme, root: 'theme')
+        render json: ThemeWithEmbeddedUploadsSerializer.new(@theme, root: 'theme')
       end
     end
 

app/serializers/theme_serializer.rb

@@ -91,3 +91,7 @@ class ThemeFieldWithEmbeddedUploadsSerializer < ThemeFieldSerializer
     Base64.encode64(raw)
   end
 end
+
+class ThemeWithEmbeddedUploadsSerializer < ThemeSerializer
+  has_many :theme_fields, serializer: ThemeFieldWithEmbeddedUploadsSerializer, embed: :objects
+end

app/serializers/theme_with_embedded_uploads_serializer.rb

@@ -1,3 +0,0 @@
-class ThemeWithEmbeddedUploadsSerializer < ThemeSerializer
-  has_many :theme_fields, serializer: ThemeFieldWithEmbeddedUploadsSerializer, embed: :objects
-end