private void removeSyncExpiration(ClassicGroup group) {
        group.clearPendingSyncMembers();
        timer.cancel(classicGroupSyncKey(group.groupId()));
    }
Remove the sync key from the timer and clear all pending sync members from the group.
Invoked when a new rebalance is triggered.

@param group  The group.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupMetadataManager.java