public void decrementNumClassicGroups(ClassicGroupState state) {
        AtomicLong counter = classicGroupGauges.get(state);
        if (counter != null) {
            counter.decrementAndGet();
        }
    }
Decrement the number of classic groups.

@param state the classic group state.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/metrics/GroupCoordinatorMetricsShard.java