Fix atom sink typo causing ClassCastException

`atom-sink` has a typo which causes a `ClassCastException` for any use of it, for example:

```clojure
(use 'lamina.core)
(atom-sink (channel 1 2 3))
  => ClassCastException lamina.core.channel$channel cannot be cast to lamina.core.channel.IChannel  lamina.core.channel/receive-all (channel.clj:253)
```