Update watermill-kafka to use sarama v1.26.4

[cikupin]

Dear watermill team,

I think that watermill-kafka should be upgraded to use sarama version 1.26.4.

As stated in sarama v1.26.0 release note, we should not use this version anymore. Version 1.26.4 should be used instead. https://github.com/Shopify/sarama/releases/tag/v1.26.0 . Or maybe you can use version the current latest version (v1.27.2)