Fixing Amazon uploads to not be hardcoded to https

Amazon S3 uploads are currently hardcoded to use https, where they should probably use whatever protocol the rest of the site is using. Removing the protocol and just using "//" links should accomplish that.

app/models/upload.rb

@@ -57,7 +57,7 @@ class Upload < ActiveRecord::Base
                                   public: true,
                                   content_type: file.content_type)
     upload.width, upload.height = ImageSizer.resize(*image_info.size)
-    upload.url = "https://#{SiteSetting.s3_upload_bucket}.s3.amazonaws.com#{path}/#{remote_filename}"
+    upload.url = "//#{SiteSetting.s3_upload_bucket}.s3.amazonaws.com#{path}/#{remote_filename}"
 
     upload.save