Make URI#open cross Ruby versions compatible

Inspired-by: commit 30475c5

Author: pabs3

lib/wayback_machine_downloader.rb

@@ -268,7 +268,7 @@ def download_file file_remote_info
         structure_dir_path dir_path
         open(file_path, "wb") do |file|
           begin
-            URI.open("https://web.archive.org/web/#{file_timestamp}id_/#{file_url}", "Accept-Encoding" => "plain") do |uri|
+            URI("https://web.archive.org/web/#{file_timestamp}id_/#{file_url}").open("Accept-Encoding" => "plain") do |uri|
               file.write(uri.read)
             end
           rescue OpenURI::HTTPError => e