fix checkstyle

Author: Technoboy-

mqtt-proxy/src/main/java/io/streamnative/pulsar/handlers/mqtt/proxy/authentication/mtls/AuthenticationProviderMTls.java

@@ -13,7 +13,6 @@
  */
 package io.streamnative.pulsar.handlers.mqtt.proxy.authentication.mtls;
 
-import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;