Gauge double registration warning for Kafka consumer metrics

[MichaelVilser]

Since #5688 we observe warnings being logged for the default kafka consumer gauge metrics such as 'kafka.consumer.fetch.manager.bytes.consumed.rate' in the form of "This Gauge has been already registered".

Stack trace of when a gauge metric is registered
1stTime_on_startup.txt
2ndTime_after_startup.txt

Looking at this function, it seems like this behavior is actually intended:

micrometer/micrometer-core/src/main/java/io/micrometer/core/instrument/binder/kafka/KafkaMetrics.java

Lines 138 to 147 in 9d650ca

	@Override
	public void bindTo(MeterRegistry registry) {
	this.registry = registry;
	commonTags = getCommonTags(registry);
	prepareToBindMetrics(registry);
	checkAndBindMetrics(registry);
	scheduler.scheduleAtFixedRate(() -> checkAndBindMetrics(registry), REFRESH_INTERVAL_MILLIS,
	REFRESH_INTERVAL_MILLIS, TimeUnit.MILLISECONDS);
	}