Add missing @Override annotation

Change-Id: I22a668b24caac64507ca076c724f6e21fa50c8e7
diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/client/ResumeImportDialog.java b/src/main/java/com/googlesource/gerrit/plugins/importer/client/ResumeImportDialog.java
index fd232a1..5b25ec4 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/importer/client/ResumeImportDialog.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/importer/client/ResumeImportDialog.java
@@ -87,6 +87,7 @@
                 p.add(new Label("Updated Changes: " + result.numChangesUpdated()));
                 Button okButton = new Button("OK");
                 okButton.addClickHandler(new ClickHandler() {
+                  @Override
                   public void onClick(ClickEvent event) {
                     successDialog.hide();
                   }