Fix smart HTTP transport protocol handling

[alixinne]

This fixes the smart HTTP transport implementation receive pack service to send requests to /git-receive-pack instead of /info/Refs?service=git-upload-pack.

This issue seems to stem from a bad copy-paste, because this was the only difference when comparing the traces of a git push done with git2go with the regular git client.

In case of a HTTPS push, it would before result in a HTTP 405 Method Not Allowed (at least on the Gitea instance I was testing it on), and it now works.