Log4jMessageLogger: Use EventGsonProvider instance from gerrit core

GsonParserTest class already using the EventGsonProvider instance from
gerrit core.

Change-Id: Ia32fd382020c00b06f7d4cf32adc5335ab0900e1

src/main/java/com/googlesource/gerrit/plugins/multisite/Log4jMessageLogger.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/multisite/Log4jMessageLogger.java b/src/main/java/com/googlesource/gerrit/plugins/multisite/Log4jMessageLogger.java
index 7c88655..1ec8886 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/multisite/Log4jMessageLogger.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/multisite/Log4jMessageLogger.java
@@ -14,9 +14,9 @@
 
 package com.googlesource.gerrit.plugins.multisite;
 
-import com.gerritforge.gerrit.eventbroker.EventGsonProvider;
 import com.gerritforge.gerrit.eventbroker.EventMessage;
 import com.google.gerrit.extensions.systemstatus.ServerInformation;
+import com.google.gerrit.server.events.EventGsonProvider;
 import com.google.gerrit.server.util.PluginLogFile;
 import com.google.gerrit.server.util.SystemLog;
 import com.google.gson.Gson;