Use events broker 3.4.0-rc0

Align with current mutli-site version

Change-Id: Ie0cd81e53332fed90b0270e429e7ddb05e67b0e1
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
index 3616263..aaa2036 100644
--- a/external_plugin_deps.bzl
+++ b/external_plugin_deps.bzl
@@ -45,8 +45,8 @@
 
     maven_jar(
         name = "events-broker",
-        artifact = "com.gerritforge:events-broker:3.3.1",
-        sha1 = "90775e671946b20e52be3a11277d1ed33973d66e",
+        artifact = "com.gerritforge:events-broker:3.4.0-rc0",
+        sha1 = "8c34c88103d4783eb4c4decde6d93541bc1cf064",
     )
 
     maven_jar(