Update Registry documentation according to SE-0292 amendment

[mattt]

This PR makes the changes to the registry service specification described in swiftlang/swift-evolution#1410

[neonichu]

@swift-ci please smoke test

[yim-lee]

https://github.com/apple/swift-package-manager/pull/3624/files#diff-1dfed3389cc482cc6446784dd9e800e5dbab6d62356bfac3010cc1382151c4bdR602-R603

A client MAY send a GET request for a URI matching the expression /{scope}/{name}/{version}

I suggest changing the URI to /{scope}/{name}/{version}.zip since .zip is required.

[tomerd]

@mattt @yim-lee should we wait before merging these PRs to see if there are further amendments we need to make and then do all in one go?

[mattt]

@swift-ci please smoke test

[tomerd]

@yim-lee @mattt do you feel this is ready to push forward with? We would probably need a short amendment review with the community

[mattt]

@tomerd Yes, I think this is ready to go. Feel free to proceed as you see fit.

[tomerd]

@mattt I believe we would need to run a short amendment review (eg https://forums.swift.org/t/amendment-se-0296-allow-overloads-that-differ-only-in-async/49808). I will make this a topic for next swift core team meeting

[tomerd]

@mattt @yim-lee amendment review: https://forums.swift.org/t/amendment-se-0292-package-registry-service/51663

[tomerd]

hi @mattt, with the amendment accepted I think we can now merge this. would you like to resolve the remaining conflicts, so I can take care of that?

[mattt]

@swift-ci Please smoke test

[mattt]

@tomerd Sure thing. That should be all of the pending feedback. Let me know if there's anything else you'd like me to do with this PR.