Remove deprecated functionality

[jirenius]

Issue

Some legacy support code for deprecated features remains even if the expired time has passed. This legacy support should be removed.

• https://github.com/resgateio/resgate/blob/master/docs/res-protocol-v1.1-update.md
• https://github.com/resgateio/resgate/blob/master/docs/res-protocol-v1.2-update.md