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

changed milestone to %Tor: 0.4.2.x-final in legacy/trac

Trac:
Parent Ticket: legacy/trac#28804 (moved)

added 041-proposed in Legacy / Trac component::core tor/tor in Legacy / Trac milestone::Tor: 0.4.2.x-final in Legacy / Trac network-team-roadmap-august in Legacy / Trac padding in Legacy / Trac parent::28804 in Legacy / Trac priority::high in Legacy / Trac resolution::implemented in Legacy / Trac scalability-roadmap in Legacy / Trac severity::normal in Legacy / Trac status::closed in Legacy / Trac tor-cell in Legacy / Trac tor-relay in Legacy / Trac tor-spec in Legacy / Trac type::task in Legacy / Trac wtf-pad in Legacy / Trac labels

asn previously reviewed this in ticket:28804#comment:19. He said the spec update piece was good.

Trac:
Cc: nickm to nickm, asn
Status: new to merge_ready

Merged; thanks!

Trac:
Status: merge_ready to closed
Priority: Medium to High
Resolution: N/A to implemented
Milestone: Tor: unspecified to Tor: 0.4.2.x-final

closed

moved from legacy/trac#31806 (moved)

added Task label and removed 1 deleted label

added Padding Relay Specifications labels and removed 1 deleted label