Each reconciliation getZookeeperSessionTimeoutSeconds() is called from here. It is a deprecated property, thus the warning is printed.
**2021-07-21 11:05:01 WARN AbstractOperator:94 - Reconciliation #7(timer) Kafka(myproject/my-cluster-1): In API version kafka.strimzi.io/v1beta2 the zookeeperSessionTimeoutSeconds property at path spec.entityOperator.userOperator.zookeeperSessionTimeoutSeconds has been deprecated. This property has been deprecated because ZooKeeper is not used anymore by the User Operator.