delete unused 04-channel version functions (#1636) (#1638)

* delete unused code and associated tests

* Update CHANGELOG.md

(cherry picked from commit 6c4a442)

Co-authored-by: Carlos Rodriguez <carlos@interchain.io>

Author: mergify[bot]

CHANGELOG.md

@@ -51,6 +51,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (apps/27-interchain-accounts)[\#1565](https://github.com/cosmos/ibc-go/pull/1565) Removing `NewErrorAcknowledgement` in favour of `channeltypes.NewErrorAcknowledgement`.
 * (transfer)[\#1565](https://github.com/cosmos/ibc-go/pull/1565) Removing `NewErrorAcknowledgement` in favour of `channeltypes.NewErrorAcknowledgement`.
 * (channel)[\#1565](https://github.com/cosmos/ibc-go/pull/1565) Updating `NewErrorAcknowledgement` to accept an error instead of a string and removing the possibility of non-deterministic writes to application state.
+* (core/04-channel)[\#1636](https://github.com/cosmos/ibc-go/pull/1636) Removing `SplitChannelVersion` and `MergeChannelVersions` functions since they are not used.
 
 ### State Machine Breaking