Fix issue with message serialisation

Use EventGsonProvider from events-broker library instead of Gerrit core.
EventGsonProvider from Gerrit core doesn't handle events provided by
plugins. This issue is fixed in stable-3.4.

Bug: Issue 14390
Change-Id: Ia0dbe8848f3860709b8b038d45ce814f7609d126

src/main/java/com/googlesource/gerrit/plugins/pubsub/Module.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/pubsub/Module.java b/src/main/java/com/googlesource/gerrit/plugins/pubsub/Module.java
index 82e6133..32110dd 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/pubsub/Module.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/pubsub/Module.java
@@ -14,11 +14,11 @@
 
 package com.googlesource.gerrit.plugins.pubsub;
 
+import com.gerritforge.gerrit.eventbroker.EventGsonProvider;
 import com.google.api.gax.core.CredentialsProvider;
 import com.google.gerrit.extensions.config.FactoryModule;
 import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.extensions.registration.DynamicSet;
-import com.google.gerrit.server.events.EventGsonProvider;
 import com.google.gerrit.server.events.EventListener;
 import com.google.gson.Gson;
 import com.google.inject.Inject;