Remove fs2-aws-ciris

[barryoneill]

The value that fs2-aws-ciris brings (it's one decoded class) is not worth dealing with the headache that is their dependency

e.g. the minor 2.3 -> 2.4 release https://github.com/vlovgr/ciris/releases/tag/v2.4.0 requires a move to scala 3.2.0 (binary incompatible, it appears)

Let's just drop fs2-aws-ciris.