In 3.1 we deprecated the eager rebalancing protocol and marked it for
removal in a later release. We aim to officially drop support and remove
the protocol from Streams in 4.0.
The effect of this PR is that it will no longer be possible to perform a
live upgrade Kafka Streams directly to 4.0 from version 2.3 or below.
Users will have to go through a bridge release between 2.4 - 3.9
instead.
Reviewers: Matthias J. Sax <matthias@confluent.io>