snet-sdk-js should select the channel with smallest channel_id in case of several channels.

[astroseger]

In case of several channels for the given sender and group_id, everybody (snet-cli, dApp, all SDK) should select the same channel by default.

In the current version snet-cli and dApp always select channel with smallest channel_id. We should make sure that we do it in SDK.
Please refer:
singnet/snet-dapp#223

According @vforvalerio87 (see singnet/snet-cli#254) we are not doing it JS-SDK.