Suppress warning about unused parameter in onEditMessage method

The idx parameter is not used for commit message edits.

Change-Id: I981d757114995b3c679faecd35f66175fc8a142b
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/FileTable.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/FileTable.java
index d74f799..73beeab 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/FileTable.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/change/FileTable.java
@@ -351,7 +351,7 @@
           });
     }
 
-    void onEditMessage(int idx) {
+    void onEditMessage(@SuppressWarnings("unused") int idx) {
       ChangeFileApi.getMessage(curr,
           new GerritCallback<String>() {
             @Override