Removed unused logger AbstractRestChannel (elastic#65948)

Removed unused logger in AbstractRestChannel

Author: chengyang14

server/src/main/java/org/elasticsearch/rest/AbstractRestChannel.java

@@ -18,8 +18,6 @@
  */
 package org.elasticsearch.rest;
 
-import org.apache.logging.log4j.LogManager;
-import org.apache.logging.log4j.Logger;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.io.Streams;
@@ -38,7 +36,6 @@
 
 public abstract class AbstractRestChannel implements RestChannel {
 
-    private static final Logger logger = LogManager.getLogger(AbstractRestChannel.class);
     private static final Predicate<String> INCLUDE_FILTER = f -> f.charAt(0) != '-';
     private static final Predicate<String> EXCLUDE_FILTER = INCLUDE_FILTER.negate();