Support 303 redirects when downloading via CommandLineUtil

It's an attempt to make Gitlab::HTTP redirection following behaviour
the same as OpenURI which we were using before.

lib/gitlab/import_export/command_line_util.rb

@@ -66,7 +66,7 @@ module Gitlab
           current_size = 0
 
           Gitlab::HTTP.get(url, stream_body: true, allow_object_storage: true) do |fragment|
-            if [301, 302, 307].include?(fragment.code)
+            if [301, 302, 303, 307].include?(fragment.code)
               Gitlab::Import::Logger.warn(message: "received redirect fragment", fragment_code: fragment.code)
             elsif fragment.code == 200
               current_size += fragment.bytesize

spec/lib/gitlab/import_export/command_line_util_spec.rb

@@ -114,7 +114,7 @@ RSpec.describe Gitlab::ImportExport::CommandLineUtil do
         end
       end
 
-      %w[MOVED_PERMANENTLY FOUND TEMPORARY_REDIRECT].each do |code|
+      %w[MOVED_PERMANENTLY FOUND SEE_OTHER TEMPORARY_REDIRECT].each do |code|
         context "with a redirect status code #{code}" do
           let(:status) { HTTP::Status.const_get(code, false) }