format

Author: JoeWang1127

java-sdk-logging/log4j2-extension/src/main/java/com/google/cloud/sdk/logging/SDKLoggingJsonLayout.java

@@ -51,8 +51,6 @@
 public class SDKLoggingJsonLayout extends AbstractStringLayout {
 
   private final Gson gson = new Gson();
-
-  private static final String EMPTY_STRING = "";
   private static final String TIME_STAMP = "timestamp";
   private static final String LEVEL = "level";
   private static final String LOGGER_NAME = "logger_name";