Update padding-spec.txt to cover hs circuit setup obfuscation
https://github.com/mikeperry-tor/torspec/tree/hs-padding-spec is the updated padding spec with the necessary changes. Current HEAD to merge is 479f0dc4bd2a873ab153ed0e7d7066e975069929
https://github.com/mikeperry-tor/torspec/tree/hs-padding-spec is the updated padding spec with the necessary changes. Current HEAD to merge is 479f0dc4bd2a873ab153ed0e7d7066e975069929