Switch back to using a tag of ably-cocoa

[lawrence-forooghian]

i.e. undo #81. This needs to be done before we release Chat.

┆Issue is synchronized with this Jira Story by Unito

[maratal]

There is a lot happening apart from switching to main, should it be reversed too? @lawrence-forooghian

[lawrence-forooghian]

No — we just want to do a release of ably-cocoa and then switch chat-swift to use this version instead of main.