Adapt to upstream gerrit event interface change

Since I9e4c8bffa the change.number is an int rather than a String.

Change-Id: Ia70982cdc3f0d9f5f68253be399176c4b32356e6
diff --git a/src/main/java/com/googlesource/gerrit/plugins/reviewers/ChangeEventListener.java b/src/main/java/com/googlesource/gerrit/plugins/reviewers/ChangeEventListener.java
index e4c5771..38111de 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/reviewers/ChangeEventListener.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/reviewers/ChangeEventListener.java
@@ -133,7 +133,7 @@
         RevWalk rw = new RevWalk(git);
         ReviewDb reviewDb = schemaFactory.open()) {
       ChangeData changeData = changeDataFactory.create(
-          reviewDb, projectName, new Change.Id(Integer.parseInt(c.number)));
+          reviewDb, projectName, new Change.Id(c.number));
       Set<String> reviewers = findReviewers(sections, changeData);
       if (reviewers.isEmpty()) {
         return;