remove unused imports

Author: yaauie

logstash-core/src/main/java/org/logstash/instrument/metrics/timer/ConcurrentLiveTimerMetric.java

@@ -1,13 +1,8 @@
 package org.logstash.instrument.metrics.timer;
 
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
 import org.logstash.instrument.metrics.AbstractMetric;
 
 import java.util.Objects;
-import java.util.concurrent.Executors;
-import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.atomic.LongAdder;
 import java.util.function.LongSupplier;